linux/fs/btrfs/backref.c
Josef Bacik 38e3eebff6 btrfs: honor path->skip_locking in backref code
Qgroups will do the old roots lookup at delayed ref time, which could be
while walking down the extent root while running a delayed ref.  This
should be fine, except we specifically lock eb's in the backref walking
code irrespective of path->skip_locking, which deadlocks the system.
Fix up the backref code to honor path->skip_locking, nobody will be
modifying the commit_root when we're searching so it's completely safe
to do.

This happens since fb235dc06f ("btrfs: qgroup: Move half of the qgroup
accounting time out of commit trans"), kernel may lockup with quota
enabled.

There is one backref trace triggered by snapshot dropping along with
write operation in the source subvolume.  The example can be reliably
reproduced:

  btrfs-cleaner   D    0  4062      2 0x80000000
  Call Trace:
   schedule+0x32/0x90
   btrfs_tree_read_lock+0x93/0x130 [btrfs]
   find_parent_nodes+0x29b/0x1170 [btrfs]
   btrfs_find_all_roots_safe+0xa8/0x120 [btrfs]
   btrfs_find_all_roots+0x57/0x70 [btrfs]
   btrfs_qgroup_trace_extent_post+0x37/0x70 [btrfs]
   btrfs_qgroup_trace_leaf_items+0x10b/0x140 [btrfs]
   btrfs_qgroup_trace_subtree+0xc8/0xe0 [btrfs]
   do_walk_down+0x541/0x5e3 [btrfs]
   walk_down_tree+0xab/0xe7 [btrfs]
   btrfs_drop_snapshot+0x356/0x71a [btrfs]
   btrfs_clean_one_deleted_snapshot+0xb8/0xf0 [btrfs]
   cleaner_kthread+0x12b/0x160 [btrfs]
   kthread+0x112/0x130
   ret_from_fork+0x27/0x50

When dropping snapshots with qgroup enabled, we will trigger backref
walk.

However such backref walk at that timing is pretty dangerous, as if one
of the parent nodes get WRITE locked by other thread, we could cause a
dead lock.

For example:

           FS 260     FS 261 (Dropped)
            node A        node B
           /      \      /      \
       node C      node D      node E
      /   \         /  \        /     \
  leaf F|leaf G|leaf H|leaf I|leaf J|leaf K

The lock sequence would be:

      Thread A (cleaner)             |       Thread B (other writer)
-----------------------------------------------------------------------
write_lock(B)                        |
write_lock(D)                        |
^^^ called by walk_down_tree()       |
                                     |       write_lock(A)
                                     |       write_lock(D) << Stall
read_lock(H) << for backref walk     |
read_lock(D) << lock owner is        |
                the same thread A    |
                so read lock is OK   |
read_lock(A) << Stall                |

So thread A hold write lock D, and needs read lock A to unlock.
While thread B holds write lock A, while needs lock D to unlock.

This will cause a deadlock.

This is not only limited to snapshot dropping case.  As the backref
walk, even only happens on commit trees, is breaking the normal top-down
locking order, makes it deadlock prone.

Fixes: fb235dc06f ("btrfs: qgroup: Move half of the qgroup accounting time out of commit trans")
CC: stable@vger.kernel.org # 4.14+
Reported-and-tested-by: David Sterba <dsterba@suse.com>
Reported-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Filipe Manana <fdmanana@suse.com>
[ rebase to latest branch and fix lock assert bug in btrfs/007 ]
Signed-off-by: Qu Wenruo <wqu@suse.com>
[ copy logs and deadlock analysis from Qu's patch ]
Signed-off-by: David Sterba <dsterba@suse.com>
2019-02-25 14:13:39 +01:00

2250 lines
59 KiB
C

// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (C) 2011 STRATO. All rights reserved.
*/
#include <linux/mm.h>
#include <linux/rbtree.h>
#include <trace/events/btrfs.h>
#include "ctree.h"
#include "disk-io.h"
#include "backref.h"
#include "ulist.h"
#include "transaction.h"
#include "delayed-ref.h"
#include "locking.h"
/* Just an arbitrary number so we can be sure this happened */
#define BACKREF_FOUND_SHARED 6
struct extent_inode_elem {
u64 inum;
u64 offset;
struct extent_inode_elem *next;
};
static int check_extent_in_eb(const struct btrfs_key *key,
const struct extent_buffer *eb,
const struct btrfs_file_extent_item *fi,
u64 extent_item_pos,
struct extent_inode_elem **eie,
bool ignore_offset)
{
u64 offset = 0;
struct extent_inode_elem *e;
if (!ignore_offset &&
!btrfs_file_extent_compression(eb, fi) &&
!btrfs_file_extent_encryption(eb, fi) &&
!btrfs_file_extent_other_encoding(eb, fi)) {
u64 data_offset;
u64 data_len;
data_offset = btrfs_file_extent_offset(eb, fi);
data_len = btrfs_file_extent_num_bytes(eb, fi);
if (extent_item_pos < data_offset ||
extent_item_pos >= data_offset + data_len)
return 1;
offset = extent_item_pos - data_offset;
}
e = kmalloc(sizeof(*e), GFP_NOFS);
if (!e)
return -ENOMEM;
e->next = *eie;
e->inum = key->objectid;
e->offset = key->offset + offset;
*eie = e;
return 0;
}
static void free_inode_elem_list(struct extent_inode_elem *eie)
{
struct extent_inode_elem *eie_next;
for (; eie; eie = eie_next) {
eie_next = eie->next;
kfree(eie);
}
}
static int find_extent_in_eb(const struct extent_buffer *eb,
u64 wanted_disk_byte, u64 extent_item_pos,
struct extent_inode_elem **eie,
bool ignore_offset)
{
u64 disk_byte;
struct btrfs_key key;
struct btrfs_file_extent_item *fi;
int slot;
int nritems;
int extent_type;
int ret;
/*
* from the shared data ref, we only have the leaf but we need
* the key. thus, we must look into all items and see that we
* find one (some) with a reference to our extent item.
*/
nritems = btrfs_header_nritems(eb);
for (slot = 0; slot < nritems; ++slot) {
btrfs_item_key_to_cpu(eb, &key, slot);
if (key.type != BTRFS_EXTENT_DATA_KEY)
continue;
fi = btrfs_item_ptr(eb, slot, struct btrfs_file_extent_item);
extent_type = btrfs_file_extent_type(eb, fi);
if (extent_type == BTRFS_FILE_EXTENT_INLINE)
continue;
/* don't skip BTRFS_FILE_EXTENT_PREALLOC, we can handle that */
disk_byte = btrfs_file_extent_disk_bytenr(eb, fi);
if (disk_byte != wanted_disk_byte)
continue;
ret = check_extent_in_eb(&key, eb, fi, extent_item_pos, eie, ignore_offset);
if (ret < 0)
return ret;
}
return 0;
}
struct preftree {
struct rb_root_cached root;
unsigned int count;
};
#define PREFTREE_INIT { .root = RB_ROOT_CACHED, .count = 0 }
struct preftrees {
struct preftree direct; /* BTRFS_SHARED_[DATA|BLOCK]_REF_KEY */
struct preftree indirect; /* BTRFS_[TREE_BLOCK|EXTENT_DATA]_REF_KEY */
struct preftree indirect_missing_keys;
};
/*
* Checks for a shared extent during backref search.
*
* The share_count tracks prelim_refs (direct and indirect) having a
* ref->count >0:
* - incremented when a ref->count transitions to >0
* - decremented when a ref->count transitions to <1
*/
struct share_check {
u64 root_objectid;
u64 inum;
int share_count;
};
static inline int extent_is_shared(struct share_check *sc)
{
return (sc && sc->share_count > 1) ? BACKREF_FOUND_SHARED : 0;
}
static struct kmem_cache *btrfs_prelim_ref_cache;
int __init btrfs_prelim_ref_init(void)
{
btrfs_prelim_ref_cache = kmem_cache_create("btrfs_prelim_ref",
sizeof(struct prelim_ref),
0,
SLAB_MEM_SPREAD,
NULL);
if (!btrfs_prelim_ref_cache)
return -ENOMEM;
return 0;
}
void __cold btrfs_prelim_ref_exit(void)
{
kmem_cache_destroy(btrfs_prelim_ref_cache);
}
static void free_pref(struct prelim_ref *ref)
{
kmem_cache_free(btrfs_prelim_ref_cache, ref);
}
/*
* Return 0 when both refs are for the same block (and can be merged).
* A -1 return indicates ref1 is a 'lower' block than ref2, while 1
* indicates a 'higher' block.
*/
static int prelim_ref_compare(struct prelim_ref *ref1,
struct prelim_ref *ref2)
{
if (ref1->level < ref2->level)
return -1;
if (ref1->level > ref2->level)
return 1;
if (ref1->root_id < ref2->root_id)
return -1;
if (ref1->root_id > ref2->root_id)
return 1;
if (ref1->key_for_search.type < ref2->key_for_search.type)
return -1;
if (ref1->key_for_search.type > ref2->key_for_search.type)
return 1;
if (ref1->key_for_search.objectid < ref2->key_for_search.objectid)
return -1;
if (ref1->key_for_search.objectid > ref2->key_for_search.objectid)
return 1;
if (ref1->key_for_search.offset < ref2->key_for_search.offset)
return -1;
if (ref1->key_for_search.offset > ref2->key_for_search.offset)
return 1;
if (ref1->parent < ref2->parent)
return -1;
if (ref1->parent > ref2->parent)
return 1;
return 0;
}
static void update_share_count(struct share_check *sc, int oldcount,
int newcount)
{
if ((!sc) || (oldcount == 0 && newcount < 1))
return;
if (oldcount > 0 && newcount < 1)
sc->share_count--;
else if (oldcount < 1 && newcount > 0)
sc->share_count++;
}
/*
* Add @newref to the @root rbtree, merging identical refs.
*
* Callers should assume that newref has been freed after calling.
*/
static void prelim_ref_insert(const struct btrfs_fs_info *fs_info,
struct preftree *preftree,
struct prelim_ref *newref,
struct share_check *sc)
{
struct rb_root_cached *root;
struct rb_node **p;
struct rb_node *parent = NULL;
struct prelim_ref *ref;
int result;
bool leftmost = true;
root = &preftree->root;
p = &root->rb_root.rb_node;
while (*p) {
parent = *p;
ref = rb_entry(parent, struct prelim_ref, rbnode);
result = prelim_ref_compare(ref, newref);
if (result < 0) {
p = &(*p)->rb_left;
} else if (result > 0) {
p = &(*p)->rb_right;
leftmost = false;
} else {
/* Identical refs, merge them and free @newref */
struct extent_inode_elem *eie = ref->inode_list;
while (eie && eie->next)
eie = eie->next;
if (!eie)
ref->inode_list = newref->inode_list;
else
eie->next = newref->inode_list;
trace_btrfs_prelim_ref_merge(fs_info, ref, newref,
preftree->count);
/*
* A delayed ref can have newref->count < 0.
* The ref->count is updated to follow any
* BTRFS_[ADD|DROP]_DELAYED_REF actions.
*/
update_share_count(sc, ref->count,
ref->count + newref->count);
ref->count += newref->count;
free_pref(newref);
return;
}
}
update_share_count(sc, 0, newref->count);
preftree->count++;
trace_btrfs_prelim_ref_insert(fs_info, newref, NULL, preftree->count);
rb_link_node(&newref->rbnode, parent, p);
rb_insert_color_cached(&newref->rbnode, root, leftmost);
}
/*
* Release the entire tree. We don't care about internal consistency so
* just free everything and then reset the tree root.
*/
static void prelim_release(struct preftree *preftree)
{
struct prelim_ref *ref, *next_ref;
rbtree_postorder_for_each_entry_safe(ref, next_ref,
&preftree->root.rb_root, rbnode)
free_pref(ref);
preftree->root = RB_ROOT_CACHED;
preftree->count = 0;
}
/*
* the rules for all callers of this function are:
* - obtaining the parent is the goal
* - if you add a key, you must know that it is a correct key
* - if you cannot add the parent or a correct key, then we will look into the
* block later to set a correct key
*
* delayed refs
* ============
* backref type | shared | indirect | shared | indirect
* information | tree | tree | data | data
* --------------------+--------+----------+--------+----------
* parent logical | y | - | - | -
* key to resolve | - | y | y | y
* tree block logical | - | - | - | -
* root for resolving | y | y | y | y
*
* - column 1: we've the parent -> done
* - column 2, 3, 4: we use the key to find the parent
*
* on disk refs (inline or keyed)
* ==============================
* backref type | shared | indirect | shared | indirect
* information | tree | tree | data | data
* --------------------+--------+----------+--------+----------
* parent logical | y | - | y | -
* key to resolve | - | - | - | y
* tree block logical | y | y | y | y
* root for resolving | - | y | y | y
*
* - column 1, 3: we've the parent -> done
* - column 2: we take the first key from the block to find the parent
* (see add_missing_keys)
* - column 4: we use the key to find the parent
*
* additional information that's available but not required to find the parent
* block might help in merging entries to gain some speed.
*/
static int add_prelim_ref(const struct btrfs_fs_info *fs_info,
struct preftree *preftree, u64 root_id,
const struct btrfs_key *key, int level, u64 parent,
u64 wanted_disk_byte, int count,
struct share_check *sc, gfp_t gfp_mask)
{
struct prelim_ref *ref;
if (root_id == BTRFS_DATA_RELOC_TREE_OBJECTID)
return 0;
ref = kmem_cache_alloc(btrfs_prelim_ref_cache, gfp_mask);
if (!ref)
return -ENOMEM;
ref->root_id = root_id;
if (key) {
ref->key_for_search = *key;
/*
* We can often find data backrefs with an offset that is too
* large (>= LLONG_MAX, maximum allowed file offset) due to
* underflows when subtracting a file's offset with the data
* offset of its corresponding extent data item. This can
* happen for example in the clone ioctl.
* So if we detect such case we set the search key's offset to
* zero to make sure we will find the matching file extent item
* at add_all_parents(), otherwise we will miss it because the
* offset taken form the backref is much larger then the offset
* of the file extent item. This can make us scan a very large
* number of file extent items, but at least it will not make
* us miss any.
* This is an ugly workaround for a behaviour that should have
* never existed, but it does and a fix for the clone ioctl
* would touch a lot of places, cause backwards incompatibility
* and would not fix the problem for extents cloned with older
* kernels.
*/
if (ref->key_for_search.type == BTRFS_EXTENT_DATA_KEY &&
ref->key_for_search.offset >= LLONG_MAX)
ref->key_for_search.offset = 0;
} else {
memset(&ref->key_for_search, 0, sizeof(ref->key_for_search));
}
ref->inode_list = NULL;
ref->level = level;
ref->count = count;
ref->parent = parent;
ref->wanted_disk_byte = wanted_disk_byte;
prelim_ref_insert(fs_info, preftree, ref, sc);
return extent_is_shared(sc);
}
/* direct refs use root == 0, key == NULL */
static int add_direct_ref(const struct btrfs_fs_info *fs_info,
struct preftrees *preftrees, int level, u64 parent,
u64 wanted_disk_byte, int count,
struct share_check *sc, gfp_t gfp_mask)
{
return add_prelim_ref(fs_info, &preftrees->direct, 0, NULL, level,
parent, wanted_disk_byte, count, sc, gfp_mask);
}
/* indirect refs use parent == 0 */
static int add_indirect_ref(const struct btrfs_fs_info *fs_info,
struct preftrees *preftrees, u64 root_id,
const struct btrfs_key *key, int level,
u64 wanted_disk_byte, int count,
struct share_check *sc, gfp_t gfp_mask)
{
struct preftree *tree = &preftrees->indirect;
if (!key)
tree = &preftrees->indirect_missing_keys;
return add_prelim_ref(fs_info, tree, root_id, key, level, 0,
wanted_disk_byte, count, sc, gfp_mask);
}
static int add_all_parents(struct btrfs_root *root, struct btrfs_path *path,
struct ulist *parents, struct prelim_ref *ref,
int level, u64 time_seq, const u64 *extent_item_pos,
u64 total_refs, bool ignore_offset)
{
int ret = 0;
int slot;
struct extent_buffer *eb;
struct btrfs_key key;
struct btrfs_key *key_for_search = &ref->key_for_search;
struct btrfs_file_extent_item *fi;
struct extent_inode_elem *eie = NULL, *old = NULL;
u64 disk_byte;
u64 wanted_disk_byte = ref->wanted_disk_byte;
u64 count = 0;
if (level != 0) {
eb = path->nodes[level];
ret = ulist_add(parents, eb->start, 0, GFP_NOFS);
if (ret < 0)
return ret;
return 0;
}
/*
* We normally enter this function with the path already pointing to
* the first item to check. But sometimes, we may enter it with
* slot==nritems. In that case, go to the next leaf before we continue.
*/
if (path->slots[0] >= btrfs_header_nritems(path->nodes[0])) {
if (time_seq == SEQ_LAST)
ret = btrfs_next_leaf(root, path);
else
ret = btrfs_next_old_leaf(root, path, time_seq);
}
while (!ret && count < total_refs) {
eb = path->nodes[0];
slot = path->slots[0];
btrfs_item_key_to_cpu(eb, &key, slot);
if (key.objectid != key_for_search->objectid ||
key.type != BTRFS_EXTENT_DATA_KEY)
break;
fi = btrfs_item_ptr(eb, slot, struct btrfs_file_extent_item);
disk_byte = btrfs_file_extent_disk_bytenr(eb, fi);
if (disk_byte == wanted_disk_byte) {
eie = NULL;
old = NULL;
count++;
if (extent_item_pos) {
ret = check_extent_in_eb(&key, eb, fi,
*extent_item_pos,
&eie, ignore_offset);
if (ret < 0)
break;
}
if (ret > 0)
goto next;
ret = ulist_add_merge_ptr(parents, eb->start,
eie, (void **)&old, GFP_NOFS);
if (ret < 0)
break;
if (!ret && extent_item_pos) {
while (old->next)
old = old->next;
old->next = eie;
}
eie = NULL;
}
next:
if (time_seq == SEQ_LAST)
ret = btrfs_next_item(root, path);
else
ret = btrfs_next_old_item(root, path, time_seq);
}
if (ret > 0)
ret = 0;
else if (ret < 0)
free_inode_elem_list(eie);
return ret;
}
/*
* resolve an indirect backref in the form (root_id, key, level)
* to a logical address
*/
static int resolve_indirect_ref(struct btrfs_fs_info *fs_info,
struct btrfs_path *path, u64 time_seq,
struct prelim_ref *ref, struct ulist *parents,
const u64 *extent_item_pos, u64 total_refs,
bool ignore_offset)
{
struct btrfs_root *root;
struct btrfs_key root_key;
struct extent_buffer *eb;
int ret = 0;
int root_level;
int level = ref->level;
int index;
root_key.objectid = ref->root_id;
root_key.type = BTRFS_ROOT_ITEM_KEY;
root_key.offset = (u64)-1;
index = srcu_read_lock(&fs_info->subvol_srcu);
root = btrfs_get_fs_root(fs_info, &root_key, false);
if (IS_ERR(root)) {
srcu_read_unlock(&fs_info->subvol_srcu, index);
ret = PTR_ERR(root);
goto out;
}
if (btrfs_is_testing(fs_info)) {
srcu_read_unlock(&fs_info->subvol_srcu, index);
ret = -ENOENT;
goto out;
}
if (path->search_commit_root)
root_level = btrfs_header_level(root->commit_root);
else if (time_seq == SEQ_LAST)
root_level = btrfs_header_level(root->node);
else
root_level = btrfs_old_root_level(root, time_seq);
if (root_level + 1 == level) {
srcu_read_unlock(&fs_info->subvol_srcu, index);
goto out;
}
path->lowest_level = level;
if (time_seq == SEQ_LAST)
ret = btrfs_search_slot(NULL, root, &ref->key_for_search, path,
0, 0);
else
ret = btrfs_search_old_slot(root, &ref->key_for_search, path,
time_seq);
/* root node has been locked, we can release @subvol_srcu safely here */
srcu_read_unlock(&fs_info->subvol_srcu, index);
btrfs_debug(fs_info,
"search slot in root %llu (level %d, ref count %d) returned %d for key (%llu %u %llu)",
ref->root_id, level, ref->count, ret,
ref->key_for_search.objectid, ref->key_for_search.type,
ref->key_for_search.offset);
if (ret < 0)
goto out;
eb = path->nodes[level];
while (!eb) {
if (WARN_ON(!level)) {
ret = 1;
goto out;
}
level--;
eb = path->nodes[level];
}
ret = add_all_parents(root, path, parents, ref, level, time_seq,
extent_item_pos, total_refs, ignore_offset);
out:
path->lowest_level = 0;
btrfs_release_path(path);
return ret;
}
static struct extent_inode_elem *
unode_aux_to_inode_list(struct ulist_node *node)
{
if (!node)
return NULL;
return (struct extent_inode_elem *)(uintptr_t)node->aux;
}
/*
* We maintain three separate rbtrees: one for direct refs, one for
* indirect refs which have a key, and one for indirect refs which do not
* have a key. Each tree does merge on insertion.
*
* Once all of the references are located, we iterate over the tree of
* indirect refs with missing keys. An appropriate key is located and
* the ref is moved onto the tree for indirect refs. After all missing
* keys are thus located, we iterate over the indirect ref tree, resolve
* each reference, and then insert the resolved reference onto the
* direct tree (merging there too).
*
* New backrefs (i.e., for parent nodes) are added to the appropriate
* rbtree as they are encountered. The new backrefs are subsequently
* resolved as above.
*/
static int resolve_indirect_refs(struct btrfs_fs_info *fs_info,
struct btrfs_path *path, u64 time_seq,
struct preftrees *preftrees,
const u64 *extent_item_pos, u64 total_refs,
struct share_check *sc, bool ignore_offset)
{
int err;
int ret = 0;
struct ulist *parents;
struct ulist_node *node;
struct ulist_iterator uiter;
struct rb_node *rnode;
parents = ulist_alloc(GFP_NOFS);
if (!parents)
return -ENOMEM;
/*
* We could trade memory usage for performance here by iterating
* the tree, allocating new refs for each insertion, and then
* freeing the entire indirect tree when we're done. In some test
* cases, the tree can grow quite large (~200k objects).
*/
while ((rnode = rb_first_cached(&preftrees->indirect.root))) {
struct prelim_ref *ref;
ref = rb_entry(rnode, struct prelim_ref, rbnode);
if (WARN(ref->parent,
"BUG: direct ref found in indirect tree")) {
ret = -EINVAL;
goto out;
}
rb_erase_cached(&ref->rbnode, &preftrees->indirect.root);
preftrees->indirect.count--;
if (ref->count == 0) {
free_pref(ref);
continue;
}
if (sc && sc->root_objectid &&
ref->root_id != sc->root_objectid) {
free_pref(ref);
ret = BACKREF_FOUND_SHARED;
goto out;
}
err = resolve_indirect_ref(fs_info, path, time_seq, ref,
parents, extent_item_pos,
total_refs, ignore_offset);
/*
* we can only tolerate ENOENT,otherwise,we should catch error
* and return directly.
*/
if (err == -ENOENT) {
prelim_ref_insert(fs_info, &preftrees->direct, ref,
NULL);
continue;
} else if (err) {
free_pref(ref);
ret = err;
goto out;
}
/* we put the first parent into the ref at hand */
ULIST_ITER_INIT(&uiter);
node = ulist_next(parents, &uiter);
ref->parent = node ? node->val : 0;
ref->inode_list = unode_aux_to_inode_list(node);
/* Add a prelim_ref(s) for any other parent(s). */
while ((node = ulist_next(parents, &uiter))) {
struct prelim_ref *new_ref;
new_ref = kmem_cache_alloc(btrfs_prelim_ref_cache,
GFP_NOFS);
if (!new_ref) {
free_pref(ref);
ret = -ENOMEM;
goto out;
}
memcpy(new_ref, ref, sizeof(*ref));
new_ref->parent = node->val;
new_ref->inode_list = unode_aux_to_inode_list(node);
prelim_ref_insert(fs_info, &preftrees->direct,
new_ref, NULL);
}
/*
* Now it's a direct ref, put it in the direct tree. We must
* do this last because the ref could be merged/freed here.
*/
prelim_ref_insert(fs_info, &preftrees->direct, ref, NULL);
ulist_reinit(parents);
cond_resched();
}
out:
ulist_free(parents);
return ret;
}
/*
* read tree blocks and add keys where required.
*/
static int add_missing_keys(struct btrfs_fs_info *fs_info,
struct preftrees *preftrees, bool lock)
{
struct prelim_ref *ref;
struct extent_buffer *eb;
struct preftree *tree = &preftrees->indirect_missing_keys;
struct rb_node *node;
while ((node = rb_first_cached(&tree->root))) {
ref = rb_entry(node, struct prelim_ref, rbnode);
rb_erase_cached(node, &tree->root);
BUG_ON(ref->parent); /* should not be a direct ref */
BUG_ON(ref->key_for_search.type);
BUG_ON(!ref->wanted_disk_byte);
eb = read_tree_block(fs_info, ref->wanted_disk_byte, 0,
ref->level - 1, NULL);
if (IS_ERR(eb)) {
free_pref(ref);
return PTR_ERR(eb);
} else if (!extent_buffer_uptodate(eb)) {
free_pref(ref);
free_extent_buffer(eb);
return -EIO;
}
if (lock)
btrfs_tree_read_lock(eb);
if (btrfs_header_level(eb) == 0)
btrfs_item_key_to_cpu(eb, &ref->key_for_search, 0);
else
btrfs_node_key_to_cpu(eb, &ref->key_for_search, 0);
if (lock)
btrfs_tree_read_unlock(eb);
free_extent_buffer(eb);
prelim_ref_insert(fs_info, &preftrees->indirect, ref, NULL);
cond_resched();
}
return 0;
}
/*
* add all currently queued delayed refs from this head whose seq nr is
* smaller or equal that seq to the list
*/
static int add_delayed_refs(const struct btrfs_fs_info *fs_info,
struct btrfs_delayed_ref_head *head, u64 seq,
struct preftrees *preftrees, u64 *total_refs,
struct share_check *sc)
{
struct btrfs_delayed_ref_node *node;
struct btrfs_delayed_extent_op *extent_op = head->extent_op;
struct btrfs_key key;
struct btrfs_key tmp_op_key;
struct rb_node *n;
int count;
int ret = 0;
if (extent_op && extent_op->update_key)
btrfs_disk_key_to_cpu(&tmp_op_key, &extent_op->key);
spin_lock(&head->lock);
for (n = rb_first_cached(&head->ref_tree); n; n = rb_next(n)) {
node = rb_entry(n, struct btrfs_delayed_ref_node,
ref_node);
if (node->seq > seq)
continue;
switch (node->action) {
case BTRFS_ADD_DELAYED_EXTENT:
case BTRFS_UPDATE_DELAYED_HEAD:
WARN_ON(1);
continue;
case BTRFS_ADD_DELAYED_REF:
count = node->ref_mod;
break;
case BTRFS_DROP_DELAYED_REF:
count = node->ref_mod * -1;
break;
default:
BUG_ON(1);
}
*total_refs += count;
switch (node->type) {
case BTRFS_TREE_BLOCK_REF_KEY: {
/* NORMAL INDIRECT METADATA backref */
struct btrfs_delayed_tree_ref *ref;
ref = btrfs_delayed_node_to_tree_ref(node);
ret = add_indirect_ref(fs_info, preftrees, ref->root,
&tmp_op_key, ref->level + 1,
node->bytenr, count, sc,
GFP_ATOMIC);
break;
}
case BTRFS_SHARED_BLOCK_REF_KEY: {
/* SHARED DIRECT METADATA backref */
struct btrfs_delayed_tree_ref *ref;
ref = btrfs_delayed_node_to_tree_ref(node);
ret = add_direct_ref(fs_info, preftrees, ref->level + 1,
ref->parent, node->bytenr, count,
sc, GFP_ATOMIC);
break;
}
case BTRFS_EXTENT_DATA_REF_KEY: {
/* NORMAL INDIRECT DATA backref */
struct btrfs_delayed_data_ref *ref;
ref = btrfs_delayed_node_to_data_ref(node);
key.objectid = ref->objectid;
key.type = BTRFS_EXTENT_DATA_KEY;
key.offset = ref->offset;
/*
* Found a inum that doesn't match our known inum, we
* know it's shared.
*/
if (sc && sc->inum && ref->objectid != sc->inum) {
ret = BACKREF_FOUND_SHARED;
goto out;
}
ret = add_indirect_ref(fs_info, preftrees, ref->root,
&key, 0, node->bytenr, count, sc,
GFP_ATOMIC);
break;
}
case BTRFS_SHARED_DATA_REF_KEY: {
/* SHARED DIRECT FULL backref */
struct btrfs_delayed_data_ref *ref;
ref = btrfs_delayed_node_to_data_ref(node);
ret = add_direct_ref(fs_info, preftrees, 0, ref->parent,
node->bytenr, count, sc,
GFP_ATOMIC);
break;
}
default:
WARN_ON(1);
}
/*
* We must ignore BACKREF_FOUND_SHARED until all delayed
* refs have been checked.
*/
if (ret && (ret != BACKREF_FOUND_SHARED))
break;
}
if (!ret)
ret = extent_is_shared(sc);
out:
spin_unlock(&head->lock);
return ret;
}
/*
* add all inline backrefs for bytenr to the list
*
* Returns 0 on success, <0 on error, or BACKREF_FOUND_SHARED.
*/
static int add_inline_refs(const struct btrfs_fs_info *fs_info,
struct btrfs_path *path, u64 bytenr,
int *info_level, struct preftrees *preftrees,
u64 *total_refs, struct share_check *sc)
{
int ret = 0;
int slot;
struct extent_buffer *leaf;
struct btrfs_key key;
struct btrfs_key found_key;
unsigned long ptr;
unsigned long end;
struct btrfs_extent_item *ei;
u64 flags;
u64 item_size;
/*
* enumerate all inline refs
*/
leaf = path->nodes[0];
slot = path->slots[0];
item_size = btrfs_item_size_nr(leaf, slot);
BUG_ON(item_size < sizeof(*ei));
ei = btrfs_item_ptr(leaf, slot, struct btrfs_extent_item);
flags = btrfs_extent_flags(leaf, ei);
*total_refs += btrfs_extent_refs(leaf, ei);
btrfs_item_key_to_cpu(leaf, &found_key, slot);
ptr = (unsigned long)(ei + 1);
end = (unsigned long)ei + item_size;
if (found_key.type == BTRFS_EXTENT_ITEM_KEY &&
flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
struct btrfs_tree_block_info *info;
info = (struct btrfs_tree_block_info *)ptr;
*info_level = btrfs_tree_block_level(leaf, info);
ptr += sizeof(struct btrfs_tree_block_info);
BUG_ON(ptr > end);
} else if (found_key.type == BTRFS_METADATA_ITEM_KEY) {
*info_level = found_key.offset;
} else {
BUG_ON(!(flags & BTRFS_EXTENT_FLAG_DATA));
}
while (ptr < end) {
struct btrfs_extent_inline_ref *iref;
u64 offset;
int type;
iref = (struct btrfs_extent_inline_ref *)ptr;
type = btrfs_get_extent_inline_ref_type(leaf, iref,
BTRFS_REF_TYPE_ANY);
if (type == BTRFS_REF_TYPE_INVALID)
return -EUCLEAN;
offset = btrfs_extent_inline_ref_offset(leaf, iref);
switch (type) {
case BTRFS_SHARED_BLOCK_REF_KEY:
ret = add_direct_ref(fs_info, preftrees,
*info_level + 1, offset,
bytenr, 1, NULL, GFP_NOFS);
break;
case BTRFS_SHARED_DATA_REF_KEY: {
struct btrfs_shared_data_ref *sdref;
int count;
sdref = (struct btrfs_shared_data_ref *)(iref + 1);
count = btrfs_shared_data_ref_count(leaf, sdref);
ret = add_direct_ref(fs_info, preftrees, 0, offset,
bytenr, count, sc, GFP_NOFS);
break;
}
case BTRFS_TREE_BLOCK_REF_KEY:
ret = add_indirect_ref(fs_info, preftrees, offset,
NULL, *info_level + 1,
bytenr, 1, NULL, GFP_NOFS);
break;
case BTRFS_EXTENT_DATA_REF_KEY: {
struct btrfs_extent_data_ref *dref;
int count;
u64 root;
dref = (struct btrfs_extent_data_ref *)(&iref->offset);
count = btrfs_extent_data_ref_count(leaf, dref);
key.objectid = btrfs_extent_data_ref_objectid(leaf,
dref);
key.type = BTRFS_EXTENT_DATA_KEY;
key.offset = btrfs_extent_data_ref_offset(leaf, dref);
if (sc && sc->inum && key.objectid != sc->inum) {
ret = BACKREF_FOUND_SHARED;
break;
}
root = btrfs_extent_data_ref_root(leaf, dref);
ret = add_indirect_ref(fs_info, preftrees, root,
&key, 0, bytenr, count,
sc, GFP_NOFS);
break;
}
default:
WARN_ON(1);
}
if (ret)
return ret;
ptr += btrfs_extent_inline_ref_size(type);
}
return 0;
}
/*
* add all non-inline backrefs for bytenr to the list
*
* Returns 0 on success, <0 on error, or BACKREF_FOUND_SHARED.
*/
static int add_keyed_refs(struct btrfs_fs_info *fs_info,
struct btrfs_path *path, u64 bytenr,
int info_level, struct preftrees *preftrees,
struct share_check *sc)
{
struct btrfs_root *extent_root = fs_info->extent_root;
int ret;
int slot;
struct extent_buffer *leaf;
struct btrfs_key key;
while (1) {
ret = btrfs_next_item(extent_root, path);
if (ret < 0)
break;
if (ret) {
ret = 0;
break;
}
slot = path->slots[0];
leaf = path->nodes[0];
btrfs_item_key_to_cpu(leaf, &key, slot);
if (key.objectid != bytenr)
break;
if (key.type < BTRFS_TREE_BLOCK_REF_KEY)
continue;
if (key.type > BTRFS_SHARED_DATA_REF_KEY)
break;
switch (key.type) {
case BTRFS_SHARED_BLOCK_REF_KEY:
/* SHARED DIRECT METADATA backref */
ret = add_direct_ref(fs_info, preftrees,
info_level + 1, key.offset,
bytenr, 1, NULL, GFP_NOFS);
break;
case BTRFS_SHARED_DATA_REF_KEY: {
/* SHARED DIRECT FULL backref */
struct btrfs_shared_data_ref *sdref;
int count;
sdref = btrfs_item_ptr(leaf, slot,
struct btrfs_shared_data_ref);
count = btrfs_shared_data_ref_count(leaf, sdref);
ret = add_direct_ref(fs_info, preftrees, 0,
key.offset, bytenr, count,
sc, GFP_NOFS);
break;
}
case BTRFS_TREE_BLOCK_REF_KEY:
/* NORMAL INDIRECT METADATA backref */
ret = add_indirect_ref(fs_info, preftrees, key.offset,
NULL, info_level + 1, bytenr,
1, NULL, GFP_NOFS);
break;
case BTRFS_EXTENT_DATA_REF_KEY: {
/* NORMAL INDIRECT DATA backref */
struct btrfs_extent_data_ref *dref;
int count;
u64 root;
dref = btrfs_item_ptr(leaf, slot,
struct btrfs_extent_data_ref);
count = btrfs_extent_data_ref_count(leaf, dref);
key.objectid = btrfs_extent_data_ref_objectid(leaf,
dref);
key.type = BTRFS_EXTENT_DATA_KEY;
key.offset = btrfs_extent_data_ref_offset(leaf, dref);
if (sc && sc->inum && key.objectid != sc->inum) {
ret = BACKREF_FOUND_SHARED;
break;
}
root = btrfs_extent_data_ref_root(leaf, dref);
ret = add_indirect_ref(fs_info, preftrees, root,
&key, 0, bytenr, count,
sc, GFP_NOFS);
break;
}
default:
WARN_ON(1);
}
if (ret)
return ret;
}
return ret;
}
/*
* this adds all existing backrefs (inline backrefs, backrefs and delayed
* refs) for the given bytenr to the refs list, merges duplicates and resolves
* indirect refs to their parent bytenr.
* When roots are found, they're added to the roots list
*
* If time_seq is set to SEQ_LAST, it will not search delayed_refs, and behave
* much like trans == NULL case, the difference only lies in it will not
* commit root.
* The special case is for qgroup to search roots in commit_transaction().
*
* @sc - if !NULL, then immediately return BACKREF_FOUND_SHARED when a
* shared extent is detected.
*
* Otherwise this returns 0 for success and <0 for an error.
*
* If ignore_offset is set to false, only extent refs whose offsets match
* extent_item_pos are returned. If true, every extent ref is returned
* and extent_item_pos is ignored.
*
* FIXME some caching might speed things up
*/
static int find_parent_nodes(struct btrfs_trans_handle *trans,
struct btrfs_fs_info *fs_info, u64 bytenr,
u64 time_seq, struct ulist *refs,
struct ulist *roots, const u64 *extent_item_pos,
struct share_check *sc, bool ignore_offset)
{
struct btrfs_key key;
struct btrfs_path *path;
struct btrfs_delayed_ref_root *delayed_refs = NULL;
struct btrfs_delayed_ref_head *head;
int info_level = 0;
int ret;
struct prelim_ref *ref;
struct rb_node *node;
struct extent_inode_elem *eie = NULL;
/* total of both direct AND indirect refs! */
u64 total_refs = 0;
struct preftrees preftrees = {
.direct = PREFTREE_INIT,
.indirect = PREFTREE_INIT,
.indirect_missing_keys = PREFTREE_INIT
};
key.objectid = bytenr;
key.offset = (u64)-1;
if (btrfs_fs_incompat(fs_info, SKINNY_METADATA))
key.type = BTRFS_METADATA_ITEM_KEY;
else
key.type = BTRFS_EXTENT_ITEM_KEY;
path = btrfs_alloc_path();
if (!path)
return -ENOMEM;
if (!trans) {
path->search_commit_root = 1;
path->skip_locking = 1;
}
if (time_seq == SEQ_LAST)
path->skip_locking = 1;
/*
* grab both a lock on the path and a lock on the delayed ref head.
* We need both to get a consistent picture of how the refs look
* at a specified point in time
*/
again:
head = NULL;
ret = btrfs_search_slot(trans, fs_info->extent_root, &key, path, 0, 0);
if (ret < 0)
goto out;
BUG_ON(ret == 0);
#ifdef CONFIG_BTRFS_FS_RUN_SANITY_TESTS
if (trans && likely(trans->type != __TRANS_DUMMY) &&
time_seq != SEQ_LAST) {
#else
if (trans && time_seq != SEQ_LAST) {
#endif
/*
* look if there are updates for this ref queued and lock the
* head
*/
delayed_refs = &trans->transaction->delayed_refs;
spin_lock(&delayed_refs->lock);
head = btrfs_find_delayed_ref_head(delayed_refs, bytenr);
if (head) {
if (!mutex_trylock(&head->mutex)) {
refcount_inc(&head->refs);
spin_unlock(&delayed_refs->lock);
btrfs_release_path(path);
/*
* Mutex was contended, block until it's
* released and try again
*/
mutex_lock(&head->mutex);
mutex_unlock(&head->mutex);
btrfs_put_delayed_ref_head(head);
goto again;
}
spin_unlock(&delayed_refs->lock);
ret = add_delayed_refs(fs_info, head, time_seq,
&preftrees, &total_refs, sc);
mutex_unlock(&head->mutex);
if (ret)
goto out;
} else {
spin_unlock(&delayed_refs->lock);
}
}
if (path->slots[0]) {
struct extent_buffer *leaf;
int slot;
path->slots[0]--;
leaf = path->nodes[0];
slot = path->slots[0];
btrfs_item_key_to_cpu(leaf, &key, slot);
if (key.objectid == bytenr &&
(key.type == BTRFS_EXTENT_ITEM_KEY ||
key.type == BTRFS_METADATA_ITEM_KEY)) {
ret = add_inline_refs(fs_info, path, bytenr,
&info_level, &preftrees,
&total_refs, sc);
if (ret)
goto out;
ret = add_keyed_refs(fs_info, path, bytenr, info_level,
&preftrees, sc);
if (ret)
goto out;
}
}
btrfs_release_path(path);
ret = add_missing_keys(fs_info, &preftrees, path->skip_locking == 0);
if (ret)
goto out;
WARN_ON(!RB_EMPTY_ROOT(&preftrees.indirect_missing_keys.root.rb_root));
ret = resolve_indirect_refs(fs_info, path, time_seq, &preftrees,
extent_item_pos, total_refs, sc, ignore_offset);
if (ret)
goto out;
WARN_ON(!RB_EMPTY_ROOT(&preftrees.indirect.root.rb_root));
/*
* This walks the tree of merged and resolved refs. Tree blocks are
* read in as needed. Unique entries are added to the ulist, and
* the list of found roots is updated.
*
* We release the entire tree in one go before returning.
*/
node = rb_first_cached(&preftrees.direct.root);
while (node) {
ref = rb_entry(node, struct prelim_ref, rbnode);
node = rb_next(&ref->rbnode);
/*
* ref->count < 0 can happen here if there are delayed
* refs with a node->action of BTRFS_DROP_DELAYED_REF.
* prelim_ref_insert() relies on this when merging
* identical refs to keep the overall count correct.
* prelim_ref_insert() will merge only those refs
* which compare identically. Any refs having
* e.g. different offsets would not be merged,
* and would retain their original ref->count < 0.
*/
if (roots && ref->count && ref->root_id && ref->parent == 0) {
if (sc && sc->root_objectid &&
ref->root_id != sc->root_objectid) {
ret = BACKREF_FOUND_SHARED;
goto out;
}
/* no parent == root of tree */
ret = ulist_add(roots, ref->root_id, 0, GFP_NOFS);
if (ret < 0)
goto out;
}
if (ref->count && ref->parent) {
if (extent_item_pos && !ref->inode_list &&
ref->level == 0) {
struct extent_buffer *eb;
eb = read_tree_block(fs_info, ref->parent, 0,
ref->level, NULL);
if (IS_ERR(eb)) {
ret = PTR_ERR(eb);
goto out;
} else if (!extent_buffer_uptodate(eb)) {
free_extent_buffer(eb);
ret = -EIO;
goto out;
}
if (!path->skip_locking) {
btrfs_tree_read_lock(eb);
btrfs_set_lock_blocking_read(eb);
}
ret = find_extent_in_eb(eb, bytenr,
*extent_item_pos, &eie, ignore_offset);
if (!path->skip_locking)
btrfs_tree_read_unlock_blocking(eb);
free_extent_buffer(eb);
if (ret < 0)
goto out;
ref->inode_list = eie;
}
ret = ulist_add_merge_ptr(refs, ref->parent,
ref->inode_list,
(void **)&eie, GFP_NOFS);
if (ret < 0)
goto out;
if (!ret && extent_item_pos) {
/*
* we've recorded that parent, so we must extend
* its inode list here
*/
BUG_ON(!eie);
while (eie->next)
eie = eie->next;
eie->next = ref->inode_list;
}
eie = NULL;
}
cond_resched();
}
out:
btrfs_free_path(path);
prelim_release(&preftrees.direct);
prelim_release(&preftrees.indirect);
prelim_release(&preftrees.indirect_missing_keys);
if (ret < 0)
free_inode_elem_list(eie);
return ret;
}
static void free_leaf_list(struct ulist *blocks)
{
struct ulist_node *node = NULL;
struct extent_inode_elem *eie;
struct ulist_iterator uiter;
ULIST_ITER_INIT(&uiter);
while ((node = ulist_next(blocks, &uiter))) {
if (!node->aux)
continue;
eie = unode_aux_to_inode_list(node);
free_inode_elem_list(eie);
node->aux = 0;
}
ulist_free(blocks);
}
/*
* Finds all leafs with a reference to the specified combination of bytenr and
* offset. key_list_head will point to a list of corresponding keys (caller must
* free each list element). The leafs will be stored in the leafs ulist, which
* must be freed with ulist_free.
*
* returns 0 on success, <0 on error
*/
static int btrfs_find_all_leafs(struct btrfs_trans_handle *trans,
struct btrfs_fs_info *fs_info, u64 bytenr,
u64 time_seq, struct ulist **leafs,
const u64 *extent_item_pos, bool ignore_offset)
{
int ret;
*leafs = ulist_alloc(GFP_NOFS);
if (!*leafs)
return -ENOMEM;
ret = find_parent_nodes(trans, fs_info, bytenr, time_seq,
*leafs, NULL, extent_item_pos, NULL, ignore_offset);
if (ret < 0 && ret != -ENOENT) {
free_leaf_list(*leafs);
return ret;
}
return 0;
}
/*
* walk all backrefs for a given extent to find all roots that reference this
* extent. Walking a backref means finding all extents that reference this
* extent and in turn walk the backrefs of those, too. Naturally this is a
* recursive process, but here it is implemented in an iterative fashion: We
* find all referencing extents for the extent in question and put them on a
* list. In turn, we find all referencing extents for those, further appending
* to the list. The way we iterate the list allows adding more elements after
* the current while iterating. The process stops when we reach the end of the
* list. Found roots are added to the roots list.
*
* returns 0 on success, < 0 on error.
*/
static int btrfs_find_all_roots_safe(struct btrfs_trans_handle *trans,
struct btrfs_fs_info *fs_info, u64 bytenr,
u64 time_seq, struct ulist **roots,
bool ignore_offset)
{
struct ulist *tmp;
struct ulist_node *node = NULL;
struct ulist_iterator uiter;
int ret;
tmp = ulist_alloc(GFP_NOFS);
if (!tmp)
return -ENOMEM;
*roots = ulist_alloc(GFP_NOFS);
if (!*roots) {
ulist_free(tmp);
return -ENOMEM;
}
ULIST_ITER_INIT(&uiter);
while (1) {
ret = find_parent_nodes(trans, fs_info, bytenr, time_seq,
tmp, *roots, NULL, NULL, ignore_offset);
if (ret < 0 && ret != -ENOENT) {
ulist_free(tmp);
ulist_free(*roots);
return ret;
}
node = ulist_next(tmp, &uiter);
if (!node)
break;
bytenr = node->val;
cond_resched();
}
ulist_free(tmp);
return 0;
}
int btrfs_find_all_roots(struct btrfs_trans_handle *trans,
struct btrfs_fs_info *fs_info, u64 bytenr,
u64 time_seq, struct ulist **roots,
bool ignore_offset)
{
int ret;
if (!trans)
down_read(&fs_info->commit_root_sem);
ret = btrfs_find_all_roots_safe(trans, fs_info, bytenr,
time_seq, roots, ignore_offset);
if (!trans)
up_read(&fs_info->commit_root_sem);
return ret;
}
/**
* btrfs_check_shared - tell us whether an extent is shared
*
* btrfs_check_shared uses the backref walking code but will short
* circuit as soon as it finds a root or inode that doesn't match the
* one passed in. This provides a significant performance benefit for
* callers (such as fiemap) which want to know whether the extent is
* shared but do not need a ref count.
*
* This attempts to allocate a transaction in order to account for
* delayed refs, but continues on even when the alloc fails.
*
* Return: 0 if extent is not shared, 1 if it is shared, < 0 on error.
*/
int btrfs_check_shared(struct btrfs_root *root, u64 inum, u64 bytenr)
{
struct btrfs_fs_info *fs_info = root->fs_info;
struct btrfs_trans_handle *trans;
struct ulist *tmp = NULL;
struct ulist *roots = NULL;
struct ulist_iterator uiter;
struct ulist_node *node;
struct seq_list elem = SEQ_LIST_INIT(elem);
int ret = 0;
struct share_check shared = {
.root_objectid = root->root_key.objectid,
.inum = inum,
.share_count = 0,
};
tmp = ulist_alloc(GFP_NOFS);
roots = ulist_alloc(GFP_NOFS);
if (!tmp || !roots) {
ulist_free(tmp);
ulist_free(roots);
return -ENOMEM;
}
trans = btrfs_join_transaction(root);
if (IS_ERR(trans)) {
trans = NULL;
down_read(&fs_info->commit_root_sem);
} else {
btrfs_get_tree_mod_seq(fs_info, &elem);
}
ULIST_ITER_INIT(&uiter);
while (1) {
ret = find_parent_nodes(trans, fs_info, bytenr, elem.seq, tmp,
roots, NULL, &shared, false);
if (ret == BACKREF_FOUND_SHARED) {
/* this is the only condition under which we return 1 */
ret = 1;
break;
}
if (ret < 0 && ret != -ENOENT)
break;
ret = 0;
node = ulist_next(tmp, &uiter);
if (!node)
break;
bytenr = node->val;
shared.share_count = 0;
cond_resched();
}
if (trans) {
btrfs_put_tree_mod_seq(fs_info, &elem);
btrfs_end_transaction(trans);
} else {
up_read(&fs_info->commit_root_sem);
}
ulist_free(tmp);
ulist_free(roots);
return ret;
}
int btrfs_find_one_extref(struct btrfs_root *root, u64 inode_objectid,
u64 start_off, struct btrfs_path *path,
struct btrfs_inode_extref **ret_extref,
u64 *found_off)
{
int ret, slot;
struct btrfs_key key;
struct btrfs_key found_key;
struct btrfs_inode_extref *extref;
const struct extent_buffer *leaf;
unsigned long ptr;
key.objectid = inode_objectid;
key.type = BTRFS_INODE_EXTREF_KEY;
key.offset = start_off;
ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
if (ret < 0)
return ret;
while (1) {
leaf = path->nodes[0];
slot = path->slots[0];
if (slot >= btrfs_header_nritems(leaf)) {
/*
* If the item at offset is not found,
* btrfs_search_slot will point us to the slot
* where it should be inserted. In our case
* that will be the slot directly before the
* next INODE_REF_KEY_V2 item. In the case
* that we're pointing to the last slot in a
* leaf, we must move one leaf over.
*/
ret = btrfs_next_leaf(root, path);
if (ret) {
if (ret >= 1)
ret = -ENOENT;
break;
}
continue;
}
btrfs_item_key_to_cpu(leaf, &found_key, slot);
/*
* Check that we're still looking at an extended ref key for
* this particular objectid. If we have different
* objectid or type then there are no more to be found
* in the tree and we can exit.
*/
ret = -ENOENT;
if (found_key.objectid != inode_objectid)
break;
if (found_key.type != BTRFS_INODE_EXTREF_KEY)
break;
ret = 0;
ptr = btrfs_item_ptr_offset(leaf, path->slots[0]);
extref = (struct btrfs_inode_extref *)ptr;
*ret_extref = extref;
if (found_off)
*found_off = found_key.offset;
break;
}
return ret;
}
/*
* this iterates to turn a name (from iref/extref) into a full filesystem path.
* Elements of the path are separated by '/' and the path is guaranteed to be
* 0-terminated. the path is only given within the current file system.
* Therefore, it never starts with a '/'. the caller is responsible to provide
* "size" bytes in "dest". the dest buffer will be filled backwards. finally,
* the start point of the resulting string is returned. this pointer is within
* dest, normally.
* in case the path buffer would overflow, the pointer is decremented further
* as if output was written to the buffer, though no more output is actually
* generated. that way, the caller can determine how much space would be
* required for the path to fit into the buffer. in that case, the returned
* value will be smaller than dest. callers must check this!
*/
char *btrfs_ref_to_path(struct btrfs_root *fs_root, struct btrfs_path *path,
u32 name_len, unsigned long name_off,
struct extent_buffer *eb_in, u64 parent,
char *dest, u32 size)
{
int slot;
u64 next_inum;
int ret;
s64 bytes_left = ((s64)size) - 1;
struct extent_buffer *eb = eb_in;
struct btrfs_key found_key;
int leave_spinning = path->leave_spinning;
struct btrfs_inode_ref *iref;
if (bytes_left >= 0)
dest[bytes_left] = '\0';
path->leave_spinning = 1;
while (1) {
bytes_left -= name_len;
if (bytes_left >= 0)
read_extent_buffer(eb, dest + bytes_left,
name_off, name_len);
if (eb != eb_in) {
if (!path->skip_locking)
btrfs_tree_read_unlock_blocking(eb);
free_extent_buffer(eb);
}
ret = btrfs_find_item(fs_root, path, parent, 0,
BTRFS_INODE_REF_KEY, &found_key);
if (ret > 0)
ret = -ENOENT;
if (ret)
break;
next_inum = found_key.offset;
/* regular exit ahead */
if (parent == next_inum)
break;
slot = path->slots[0];
eb = path->nodes[0];
/* make sure we can use eb after releasing the path */
if (eb != eb_in) {
if (!path->skip_locking)
btrfs_set_lock_blocking_read(eb);
path->nodes[0] = NULL;
path->locks[0] = 0;
}
btrfs_release_path(path);
iref = btrfs_item_ptr(eb, slot, struct btrfs_inode_ref);
name_len = btrfs_inode_ref_name_len(eb, iref);
name_off = (unsigned long)(iref + 1);
parent = next_inum;
--bytes_left;
if (bytes_left >= 0)
dest[bytes_left] = '/';
}
btrfs_release_path(path);
path->leave_spinning = leave_spinning;
if (ret)
return ERR_PTR(ret);
return dest + bytes_left;
}
/*
* this makes the path point to (logical EXTENT_ITEM *)
* returns BTRFS_EXTENT_FLAG_DATA for data, BTRFS_EXTENT_FLAG_TREE_BLOCK for
* tree blocks and <0 on error.
*/
int extent_from_logical(struct btrfs_fs_info *fs_info, u64 logical,
struct btrfs_path *path, struct btrfs_key *found_key,
u64 *flags_ret)
{
int ret;
u64 flags;
u64 size = 0;
u32 item_size;
const struct extent_buffer *eb;
struct btrfs_extent_item *ei;
struct btrfs_key key;
if (btrfs_fs_incompat(fs_info, SKINNY_METADATA))
key.type = BTRFS_METADATA_ITEM_KEY;
else
key.type = BTRFS_EXTENT_ITEM_KEY;
key.objectid = logical;
key.offset = (u64)-1;
ret = btrfs_search_slot(NULL, fs_info->extent_root, &key, path, 0, 0);
if (ret < 0)
return ret;
ret = btrfs_previous_extent_item(fs_info->extent_root, path, 0);
if (ret) {
if (ret > 0)
ret = -ENOENT;
return ret;
}
btrfs_item_key_to_cpu(path->nodes[0], found_key, path->slots[0]);
if (found_key->type == BTRFS_METADATA_ITEM_KEY)
size = fs_info->nodesize;
else if (found_key->type == BTRFS_EXTENT_ITEM_KEY)
size = found_key->offset;
if (found_key->objectid > logical ||
found_key->objectid + size <= logical) {
btrfs_debug(fs_info,
"logical %llu is not within any extent", logical);
return -ENOENT;
}
eb = path->nodes[0];
item_size = btrfs_item_size_nr(eb, path->slots[0]);
BUG_ON(item_size < sizeof(*ei));
ei = btrfs_item_ptr(eb, path->slots[0], struct btrfs_extent_item);
flags = btrfs_extent_flags(eb, ei);
btrfs_debug(fs_info,
"logical %llu is at position %llu within the extent (%llu EXTENT_ITEM %llu) flags %#llx size %u",
logical, logical - found_key->objectid, found_key->objectid,
found_key->offset, flags, item_size);
WARN_ON(!flags_ret);
if (flags_ret) {
if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK)
*flags_ret = BTRFS_EXTENT_FLAG_TREE_BLOCK;
else if (flags & BTRFS_EXTENT_FLAG_DATA)
*flags_ret = BTRFS_EXTENT_FLAG_DATA;
else
BUG_ON(1);
return 0;
}
return -EIO;
}
/*
* helper function to iterate extent inline refs. ptr must point to a 0 value
* for the first call and may be modified. it is used to track state.
* if more refs exist, 0 is returned and the next call to
* get_extent_inline_ref must pass the modified ptr parameter to get the
* next ref. after the last ref was processed, 1 is returned.
* returns <0 on error
*/
static int get_extent_inline_ref(unsigned long *ptr,
const struct extent_buffer *eb,
const struct btrfs_key *key,
const struct btrfs_extent_item *ei,
u32 item_size,
struct btrfs_extent_inline_ref **out_eiref,
int *out_type)
{
unsigned long end;
u64 flags;
struct btrfs_tree_block_info *info;
if (!*ptr) {
/* first call */
flags = btrfs_extent_flags(eb, ei);
if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
if (key->type == BTRFS_METADATA_ITEM_KEY) {
/* a skinny metadata extent */
*out_eiref =
(struct btrfs_extent_inline_ref *)(ei + 1);
} else {
WARN_ON(key->type != BTRFS_EXTENT_ITEM_KEY);
info = (struct btrfs_tree_block_info *)(ei + 1);
*out_eiref =
(struct btrfs_extent_inline_ref *)(info + 1);
}
} else {
*out_eiref = (struct btrfs_extent_inline_ref *)(ei + 1);
}
*ptr = (unsigned long)*out_eiref;
if ((unsigned long)(*ptr) >= (unsigned long)ei + item_size)
return -ENOENT;
}
end = (unsigned long)ei + item_size;
*out_eiref = (struct btrfs_extent_inline_ref *)(*ptr);
*out_type = btrfs_get_extent_inline_ref_type(eb, *out_eiref,
BTRFS_REF_TYPE_ANY);
if (*out_type == BTRFS_REF_TYPE_INVALID)
return -EUCLEAN;
*ptr += btrfs_extent_inline_ref_size(*out_type);
WARN_ON(*ptr > end);
if (*ptr == end)
return 1; /* last */
return 0;
}
/*
* reads the tree block backref for an extent. tree level and root are returned
* through out_level and out_root. ptr must point to a 0 value for the first
* call and may be modified (see get_extent_inline_ref comment).
* returns 0 if data was provided, 1 if there was no more data to provide or
* <0 on error.
*/
int tree_backref_for_extent(unsigned long *ptr, struct extent_buffer *eb,
struct btrfs_key *key, struct btrfs_extent_item *ei,
u32 item_size, u64 *out_root, u8 *out_level)
{
int ret;
int type;
struct btrfs_extent_inline_ref *eiref;
if (*ptr == (unsigned long)-1)
return 1;
while (1) {
ret = get_extent_inline_ref(ptr, eb, key, ei, item_size,
&eiref, &type);
if (ret < 0)
return ret;
if (type == BTRFS_TREE_BLOCK_REF_KEY ||
type == BTRFS_SHARED_BLOCK_REF_KEY)
break;
if (ret == 1)
return 1;
}
/* we can treat both ref types equally here */
*out_root = btrfs_extent_inline_ref_offset(eb, eiref);
if (key->type == BTRFS_EXTENT_ITEM_KEY) {
struct btrfs_tree_block_info *info;
info = (struct btrfs_tree_block_info *)(ei + 1);
*out_level = btrfs_tree_block_level(eb, info);
} else {
ASSERT(key->type == BTRFS_METADATA_ITEM_KEY);
*out_level = (u8)key->offset;
}
if (ret == 1)
*ptr = (unsigned long)-1;
return 0;
}
static int iterate_leaf_refs(struct btrfs_fs_info *fs_info,
struct extent_inode_elem *inode_list,
u64 root, u64 extent_item_objectid,
iterate_extent_inodes_t *iterate, void *ctx)
{
struct extent_inode_elem *eie;
int ret = 0;
for (eie = inode_list; eie; eie = eie->next) {
btrfs_debug(fs_info,
"ref for %llu resolved, key (%llu EXTEND_DATA %llu), root %llu",
extent_item_objectid, eie->inum,
eie->offset, root);
ret = iterate(eie->inum, eie->offset, root, ctx);
if (ret) {
btrfs_debug(fs_info,
"stopping iteration for %llu due to ret=%d",
extent_item_objectid, ret);
break;
}
}
return ret;
}
/*
* calls iterate() for every inode that references the extent identified by
* the given parameters.
* when the iterator function returns a non-zero value, iteration stops.
*/
int iterate_extent_inodes(struct btrfs_fs_info *fs_info,
u64 extent_item_objectid, u64 extent_item_pos,
int search_commit_root,
iterate_extent_inodes_t *iterate, void *ctx,
bool ignore_offset)
{
int ret;
struct btrfs_trans_handle *trans = NULL;
struct ulist *refs = NULL;
struct ulist *roots = NULL;
struct ulist_node *ref_node = NULL;
struct ulist_node *root_node = NULL;
struct seq_list tree_mod_seq_elem = SEQ_LIST_INIT(tree_mod_seq_elem);
struct ulist_iterator ref_uiter;
struct ulist_iterator root_uiter;
btrfs_debug(fs_info, "resolving all inodes for extent %llu",
extent_item_objectid);
if (!search_commit_root) {
trans = btrfs_join_transaction(fs_info->extent_root);
if (IS_ERR(trans))
return PTR_ERR(trans);
btrfs_get_tree_mod_seq(fs_info, &tree_mod_seq_elem);
} else {
down_read(&fs_info->commit_root_sem);
}
ret = btrfs_find_all_leafs(trans, fs_info, extent_item_objectid,
tree_mod_seq_elem.seq, &refs,
&extent_item_pos, ignore_offset);
if (ret)
goto out;
ULIST_ITER_INIT(&ref_uiter);
while (!ret && (ref_node = ulist_next(refs, &ref_uiter))) {
ret = btrfs_find_all_roots_safe(trans, fs_info, ref_node->val,
tree_mod_seq_elem.seq, &roots,
ignore_offset);
if (ret)
break;
ULIST_ITER_INIT(&root_uiter);
while (!ret && (root_node = ulist_next(roots, &root_uiter))) {
btrfs_debug(fs_info,
"root %llu references leaf %llu, data list %#llx",
root_node->val, ref_node->val,
ref_node->aux);
ret = iterate_leaf_refs(fs_info,
(struct extent_inode_elem *)
(uintptr_t)ref_node->aux,
root_node->val,
extent_item_objectid,
iterate, ctx);
}
ulist_free(roots);
}
free_leaf_list(refs);
out:
if (!search_commit_root) {
btrfs_put_tree_mod_seq(fs_info, &tree_mod_seq_elem);
btrfs_end_transaction(trans);
} else {
up_read(&fs_info->commit_root_sem);
}
return ret;
}
int iterate_inodes_from_logical(u64 logical, struct btrfs_fs_info *fs_info,
struct btrfs_path *path,
iterate_extent_inodes_t *iterate, void *ctx,
bool ignore_offset)
{
int ret;
u64 extent_item_pos;
u64 flags = 0;
struct btrfs_key found_key;
int search_commit_root = path->search_commit_root;
ret = extent_from_logical(fs_info, logical, path, &found_key, &flags);
btrfs_release_path(path);
if (ret < 0)
return ret;
if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK)
return -EINVAL;
extent_item_pos = logical - found_key.objectid;
ret = iterate_extent_inodes(fs_info, found_key.objectid,
extent_item_pos, search_commit_root,
iterate, ctx, ignore_offset);
return ret;
}
typedef int (iterate_irefs_t)(u64 parent, u32 name_len, unsigned long name_off,
struct extent_buffer *eb, void *ctx);
static int iterate_inode_refs(u64 inum, struct btrfs_root *fs_root,
struct btrfs_path *path,
iterate_irefs_t *iterate, void *ctx)
{
int ret = 0;
int slot;
u32 cur;
u32 len;
u32 name_len;
u64 parent = 0;
int found = 0;
struct extent_buffer *eb;
struct btrfs_item *item;
struct btrfs_inode_ref *iref;
struct btrfs_key found_key;
while (!ret) {
ret = btrfs_find_item(fs_root, path, inum,
parent ? parent + 1 : 0, BTRFS_INODE_REF_KEY,
&found_key);
if (ret < 0)
break;
if (ret) {
ret = found ? 0 : -ENOENT;
break;
}
++found;
parent = found_key.offset;
slot = path->slots[0];
eb = btrfs_clone_extent_buffer(path->nodes[0]);
if (!eb) {
ret = -ENOMEM;
break;
}
btrfs_release_path(path);
item = btrfs_item_nr(slot);
iref = btrfs_item_ptr(eb, slot, struct btrfs_inode_ref);
for (cur = 0; cur < btrfs_item_size(eb, item); cur += len) {
name_len = btrfs_inode_ref_name_len(eb, iref);
/* path must be released before calling iterate()! */
btrfs_debug(fs_root->fs_info,
"following ref at offset %u for inode %llu in tree %llu",
cur, found_key.objectid,
fs_root->root_key.objectid);
ret = iterate(parent, name_len,
(unsigned long)(iref + 1), eb, ctx);
if (ret)
break;
len = sizeof(*iref) + name_len;
iref = (struct btrfs_inode_ref *)((char *)iref + len);
}
free_extent_buffer(eb);
}
btrfs_release_path(path);
return ret;
}
static int iterate_inode_extrefs(u64 inum, struct btrfs_root *fs_root,
struct btrfs_path *path,
iterate_irefs_t *iterate, void *ctx)
{
int ret;
int slot;
u64 offset = 0;
u64 parent;
int found = 0;
struct extent_buffer *eb;
struct btrfs_inode_extref *extref;
u32 item_size;
u32 cur_offset;
unsigned long ptr;
while (1) {
ret = btrfs_find_one_extref(fs_root, inum, offset, path, &extref,
&offset);
if (ret < 0)
break;
if (ret) {
ret = found ? 0 : -ENOENT;
break;
}
++found;
slot = path->slots[0];
eb = btrfs_clone_extent_buffer(path->nodes[0]);
if (!eb) {
ret = -ENOMEM;
break;
}
btrfs_release_path(path);
item_size = btrfs_item_size_nr(eb, slot);
ptr = btrfs_item_ptr_offset(eb, slot);
cur_offset = 0;
while (cur_offset < item_size) {
u32 name_len;
extref = (struct btrfs_inode_extref *)(ptr + cur_offset);
parent = btrfs_inode_extref_parent(eb, extref);
name_len = btrfs_inode_extref_name_len(eb, extref);
ret = iterate(parent, name_len,
(unsigned long)&extref->name, eb, ctx);
if (ret)
break;
cur_offset += btrfs_inode_extref_name_len(eb, extref);
cur_offset += sizeof(*extref);
}
free_extent_buffer(eb);
offset++;
}
btrfs_release_path(path);
return ret;
}
static int iterate_irefs(u64 inum, struct btrfs_root *fs_root,
struct btrfs_path *path, iterate_irefs_t *iterate,
void *ctx)
{
int ret;
int found_refs = 0;
ret = iterate_inode_refs(inum, fs_root, path, iterate, ctx);
if (!ret)
++found_refs;
else if (ret != -ENOENT)
return ret;
ret = iterate_inode_extrefs(inum, fs_root, path, iterate, ctx);
if (ret == -ENOENT && found_refs)
return 0;
return ret;
}
/*
* returns 0 if the path could be dumped (probably truncated)
* returns <0 in case of an error
*/
static int inode_to_path(u64 inum, u32 name_len, unsigned long name_off,
struct extent_buffer *eb, void *ctx)
{
struct inode_fs_paths *ipath = ctx;
char *fspath;
char *fspath_min;
int i = ipath->fspath->elem_cnt;
const int s_ptr = sizeof(char *);
u32 bytes_left;
bytes_left = ipath->fspath->bytes_left > s_ptr ?
ipath->fspath->bytes_left - s_ptr : 0;
fspath_min = (char *)ipath->fspath->val + (i + 1) * s_ptr;
fspath = btrfs_ref_to_path(ipath->fs_root, ipath->btrfs_path, name_len,
name_off, eb, inum, fspath_min, bytes_left);
if (IS_ERR(fspath))
return PTR_ERR(fspath);
if (fspath > fspath_min) {
ipath->fspath->val[i] = (u64)(unsigned long)fspath;
++ipath->fspath->elem_cnt;
ipath->fspath->bytes_left = fspath - fspath_min;
} else {
++ipath->fspath->elem_missed;
ipath->fspath->bytes_missing += fspath_min - fspath;
ipath->fspath->bytes_left = 0;
}
return 0;
}
/*
* this dumps all file system paths to the inode into the ipath struct, provided
* is has been created large enough. each path is zero-terminated and accessed
* from ipath->fspath->val[i].
* when it returns, there are ipath->fspath->elem_cnt number of paths available
* in ipath->fspath->val[]. when the allocated space wasn't sufficient, the
* number of missed paths is recorded in ipath->fspath->elem_missed, otherwise,
* it's zero. ipath->fspath->bytes_missing holds the number of bytes that would
* have been needed to return all paths.
*/
int paths_from_inode(u64 inum, struct inode_fs_paths *ipath)
{
return iterate_irefs(inum, ipath->fs_root, ipath->btrfs_path,
inode_to_path, ipath);
}
struct btrfs_data_container *init_data_container(u32 total_bytes)
{
struct btrfs_data_container *data;
size_t alloc_bytes;
alloc_bytes = max_t(size_t, total_bytes, sizeof(*data));
data = kvmalloc(alloc_bytes, GFP_KERNEL);
if (!data)
return ERR_PTR(-ENOMEM);
if (total_bytes >= sizeof(*data)) {
data->bytes_left = total_bytes - sizeof(*data);
data->bytes_missing = 0;
} else {
data->bytes_missing = sizeof(*data) - total_bytes;
data->bytes_left = 0;
}
data->elem_cnt = 0;
data->elem_missed = 0;
return data;
}
/*
* allocates space to return multiple file system paths for an inode.
* total_bytes to allocate are passed, note that space usable for actual path
* information will be total_bytes - sizeof(struct inode_fs_paths).
* the returned pointer must be freed with free_ipath() in the end.
*/
struct inode_fs_paths *init_ipath(s32 total_bytes, struct btrfs_root *fs_root,
struct btrfs_path *path)
{
struct inode_fs_paths *ifp;
struct btrfs_data_container *fspath;
fspath = init_data_container(total_bytes);
if (IS_ERR(fspath))
return ERR_CAST(fspath);
ifp = kmalloc(sizeof(*ifp), GFP_KERNEL);
if (!ifp) {
kvfree(fspath);
return ERR_PTR(-ENOMEM);
}
ifp->btrfs_path = path;
ifp->fspath = fspath;
ifp->fs_root = fs_root;
return ifp;
}
void free_ipath(struct inode_fs_paths *ipath)
{
if (!ipath)
return;
kvfree(ipath->fspath);
kfree(ipath);
}