linux/fs/btrfs/inode-map.c
Chris Mason 1bbc621ef2 Btrfs: allow block group cache writeout outside critical section in commit
We loop through all of the dirty block groups during commit and write
the free space cache.  In order to make sure the cache is currect, we do
this while no other writers are allowed in the commit.

If a large number of block groups are dirty, this can introduce long
stalls during the final stages of the commit, which can block new procs
trying to change the filesystem.

This commit changes the block group cache writeout to take appropriate
locks and allow it to run earlier in the commit.  We'll still have to
redo some of the block groups, but it means we can get most of the work
out of the way without blocking the entire FS.

Signed-off-by: Chris Mason <clm@fb.com>
2015-04-10 14:07:22 -07:00

569 lines
14 KiB
C

/*
* Copyright (C) 2007 Oracle. All rights reserved.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public
* License v2 as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public
* License along with this program; if not, write to the
* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
* Boston, MA 021110-1307, USA.
*/
#include <linux/delay.h>
#include <linux/kthread.h>
#include <linux/pagemap.h>
#include "ctree.h"
#include "disk-io.h"
#include "free-space-cache.h"
#include "inode-map.h"
#include "transaction.h"
static int caching_kthread(void *data)
{
struct btrfs_root *root = data;
struct btrfs_fs_info *fs_info = root->fs_info;
struct btrfs_free_space_ctl *ctl = root->free_ino_ctl;
struct btrfs_key key;
struct btrfs_path *path;
struct extent_buffer *leaf;
u64 last = (u64)-1;
int slot;
int ret;
if (!btrfs_test_opt(root, INODE_MAP_CACHE))
return 0;
path = btrfs_alloc_path();
if (!path)
return -ENOMEM;
/* Since the commit root is read-only, we can safely skip locking. */
path->skip_locking = 1;
path->search_commit_root = 1;
path->reada = 2;
key.objectid = BTRFS_FIRST_FREE_OBJECTID;
key.offset = 0;
key.type = BTRFS_INODE_ITEM_KEY;
again:
/* need to make sure the commit_root doesn't disappear */
down_read(&fs_info->commit_root_sem);
ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
if (ret < 0)
goto out;
while (1) {
if (btrfs_fs_closing(fs_info))
goto out;
leaf = path->nodes[0];
slot = path->slots[0];
if (slot >= btrfs_header_nritems(leaf)) {
ret = btrfs_next_leaf(root, path);
if (ret < 0)
goto out;
else if (ret > 0)
break;
if (need_resched() ||
btrfs_transaction_in_commit(fs_info)) {
leaf = path->nodes[0];
if (WARN_ON(btrfs_header_nritems(leaf) == 0))
break;
/*
* Save the key so we can advances forward
* in the next search.
*/
btrfs_item_key_to_cpu(leaf, &key, 0);
btrfs_release_path(path);
root->ino_cache_progress = last;
up_read(&fs_info->commit_root_sem);
schedule_timeout(1);
goto again;
} else
continue;
}
btrfs_item_key_to_cpu(leaf, &key, slot);
if (key.type != BTRFS_INODE_ITEM_KEY)
goto next;
if (key.objectid >= root->highest_objectid)
break;
if (last != (u64)-1 && last + 1 != key.objectid) {
__btrfs_add_free_space(ctl, last + 1,
key.objectid - last - 1);
wake_up(&root->ino_cache_wait);
}
last = key.objectid;
next:
path->slots[0]++;
}
if (last < root->highest_objectid - 1) {
__btrfs_add_free_space(ctl, last + 1,
root->highest_objectid - last - 1);
}
spin_lock(&root->ino_cache_lock);
root->ino_cache_state = BTRFS_CACHE_FINISHED;
spin_unlock(&root->ino_cache_lock);
root->ino_cache_progress = (u64)-1;
btrfs_unpin_free_ino(root);
out:
wake_up(&root->ino_cache_wait);
up_read(&fs_info->commit_root_sem);
btrfs_free_path(path);
return ret;
}
static void start_caching(struct btrfs_root *root)
{
struct btrfs_free_space_ctl *ctl = root->free_ino_ctl;
struct task_struct *tsk;
int ret;
u64 objectid;
if (!btrfs_test_opt(root, INODE_MAP_CACHE))
return;
spin_lock(&root->ino_cache_lock);
if (root->ino_cache_state != BTRFS_CACHE_NO) {
spin_unlock(&root->ino_cache_lock);
return;
}
root->ino_cache_state = BTRFS_CACHE_STARTED;
spin_unlock(&root->ino_cache_lock);
ret = load_free_ino_cache(root->fs_info, root);
if (ret == 1) {
spin_lock(&root->ino_cache_lock);
root->ino_cache_state = BTRFS_CACHE_FINISHED;
spin_unlock(&root->ino_cache_lock);
return;
}
/*
* It can be quite time-consuming to fill the cache by searching
* through the extent tree, and this can keep ino allocation path
* waiting. Therefore at start we quickly find out the highest
* inode number and we know we can use inode numbers which fall in
* [highest_ino + 1, BTRFS_LAST_FREE_OBJECTID].
*/
ret = btrfs_find_free_objectid(root, &objectid);
if (!ret && objectid <= BTRFS_LAST_FREE_OBJECTID) {
__btrfs_add_free_space(ctl, objectid,
BTRFS_LAST_FREE_OBJECTID - objectid + 1);
}
tsk = kthread_run(caching_kthread, root, "btrfs-ino-cache-%llu",
root->root_key.objectid);
if (IS_ERR(tsk)) {
btrfs_warn(root->fs_info, "failed to start inode caching task");
btrfs_clear_pending_and_info(root->fs_info, INODE_MAP_CACHE,
"disabling inode map caching");
}
}
int btrfs_find_free_ino(struct btrfs_root *root, u64 *objectid)
{
if (!btrfs_test_opt(root, INODE_MAP_CACHE))
return btrfs_find_free_objectid(root, objectid);
again:
*objectid = btrfs_find_ino_for_alloc(root);
if (*objectid != 0)
return 0;
start_caching(root);
wait_event(root->ino_cache_wait,
root->ino_cache_state == BTRFS_CACHE_FINISHED ||
root->free_ino_ctl->free_space > 0);
if (root->ino_cache_state == BTRFS_CACHE_FINISHED &&
root->free_ino_ctl->free_space == 0)
return -ENOSPC;
else
goto again;
}
void btrfs_return_ino(struct btrfs_root *root, u64 objectid)
{
struct btrfs_free_space_ctl *pinned = root->free_ino_pinned;
if (!btrfs_test_opt(root, INODE_MAP_CACHE))
return;
again:
if (root->ino_cache_state == BTRFS_CACHE_FINISHED) {
__btrfs_add_free_space(pinned, objectid, 1);
} else {
down_write(&root->fs_info->commit_root_sem);
spin_lock(&root->ino_cache_lock);
if (root->ino_cache_state == BTRFS_CACHE_FINISHED) {
spin_unlock(&root->ino_cache_lock);
up_write(&root->fs_info->commit_root_sem);
goto again;
}
spin_unlock(&root->ino_cache_lock);
start_caching(root);
__btrfs_add_free_space(pinned, objectid, 1);
up_write(&root->fs_info->commit_root_sem);
}
}
/*
* When a transaction is committed, we'll move those inode numbers which are
* smaller than root->ino_cache_progress from pinned tree to free_ino tree, and
* others will just be dropped, because the commit root we were searching has
* changed.
*
* Must be called with root->fs_info->commit_root_sem held
*/
void btrfs_unpin_free_ino(struct btrfs_root *root)
{
struct btrfs_free_space_ctl *ctl = root->free_ino_ctl;
struct rb_root *rbroot = &root->free_ino_pinned->free_space_offset;
struct btrfs_free_space *info;
struct rb_node *n;
u64 count;
if (!btrfs_test_opt(root, INODE_MAP_CACHE))
return;
while (1) {
n = rb_first(rbroot);
if (!n)
break;
info = rb_entry(n, struct btrfs_free_space, offset_index);
BUG_ON(info->bitmap); /* Logic error */
if (info->offset > root->ino_cache_progress)
goto free;
else if (info->offset + info->bytes > root->ino_cache_progress)
count = root->ino_cache_progress - info->offset + 1;
else
count = info->bytes;
__btrfs_add_free_space(ctl, info->offset, count);
free:
rb_erase(&info->offset_index, rbroot);
kfree(info);
}
}
#define INIT_THRESHOLD (((1024 * 32) / 2) / sizeof(struct btrfs_free_space))
#define INODES_PER_BITMAP (PAGE_CACHE_SIZE * 8)
/*
* The goal is to keep the memory used by the free_ino tree won't
* exceed the memory if we use bitmaps only.
*/
static void recalculate_thresholds(struct btrfs_free_space_ctl *ctl)
{
struct btrfs_free_space *info;
struct rb_node *n;
int max_ino;
int max_bitmaps;
n = rb_last(&ctl->free_space_offset);
if (!n) {
ctl->extents_thresh = INIT_THRESHOLD;
return;
}
info = rb_entry(n, struct btrfs_free_space, offset_index);
/*
* Find the maximum inode number in the filesystem. Note we
* ignore the fact that this can be a bitmap, because we are
* not doing precise calculation.
*/
max_ino = info->bytes - 1;
max_bitmaps = ALIGN(max_ino, INODES_PER_BITMAP) / INODES_PER_BITMAP;
if (max_bitmaps <= ctl->total_bitmaps) {
ctl->extents_thresh = 0;
return;
}
ctl->extents_thresh = (max_bitmaps - ctl->total_bitmaps) *
PAGE_CACHE_SIZE / sizeof(*info);
}
/*
* We don't fall back to bitmap, if we are below the extents threshold
* or this chunk of inode numbers is a big one.
*/
static bool use_bitmap(struct btrfs_free_space_ctl *ctl,
struct btrfs_free_space *info)
{
if (ctl->free_extents < ctl->extents_thresh ||
info->bytes > INODES_PER_BITMAP / 10)
return false;
return true;
}
static struct btrfs_free_space_op free_ino_op = {
.recalc_thresholds = recalculate_thresholds,
.use_bitmap = use_bitmap,
};
static void pinned_recalc_thresholds(struct btrfs_free_space_ctl *ctl)
{
}
static bool pinned_use_bitmap(struct btrfs_free_space_ctl *ctl,
struct btrfs_free_space *info)
{
/*
* We always use extents for two reasons:
*
* - The pinned tree is only used during the process of caching
* work.
* - Make code simpler. See btrfs_unpin_free_ino().
*/
return false;
}
static struct btrfs_free_space_op pinned_free_ino_op = {
.recalc_thresholds = pinned_recalc_thresholds,
.use_bitmap = pinned_use_bitmap,
};
void btrfs_init_free_ino_ctl(struct btrfs_root *root)
{
struct btrfs_free_space_ctl *ctl = root->free_ino_ctl;
struct btrfs_free_space_ctl *pinned = root->free_ino_pinned;
spin_lock_init(&ctl->tree_lock);
ctl->unit = 1;
ctl->start = 0;
ctl->private = NULL;
ctl->op = &free_ino_op;
INIT_LIST_HEAD(&ctl->trimming_ranges);
mutex_init(&ctl->cache_writeout_mutex);
/*
* Initially we allow to use 16K of ram to cache chunks of
* inode numbers before we resort to bitmaps. This is somewhat
* arbitrary, but it will be adjusted in runtime.
*/
ctl->extents_thresh = INIT_THRESHOLD;
spin_lock_init(&pinned->tree_lock);
pinned->unit = 1;
pinned->start = 0;
pinned->private = NULL;
pinned->extents_thresh = 0;
pinned->op = &pinned_free_ino_op;
}
int btrfs_save_ino_cache(struct btrfs_root *root,
struct btrfs_trans_handle *trans)
{
struct btrfs_free_space_ctl *ctl = root->free_ino_ctl;
struct btrfs_path *path;
struct inode *inode;
struct btrfs_block_rsv *rsv;
u64 num_bytes;
u64 alloc_hint = 0;
int ret;
int prealloc;
bool retry = false;
/* only fs tree and subvol/snap needs ino cache */
if (root->root_key.objectid != BTRFS_FS_TREE_OBJECTID &&
(root->root_key.objectid < BTRFS_FIRST_FREE_OBJECTID ||
root->root_key.objectid > BTRFS_LAST_FREE_OBJECTID))
return 0;
/* Don't save inode cache if we are deleting this root */
if (btrfs_root_refs(&root->root_item) == 0)
return 0;
if (!btrfs_test_opt(root, INODE_MAP_CACHE))
return 0;
path = btrfs_alloc_path();
if (!path)
return -ENOMEM;
rsv = trans->block_rsv;
trans->block_rsv = &root->fs_info->trans_block_rsv;
num_bytes = trans->bytes_reserved;
/*
* 1 item for inode item insertion if need
* 4 items for inode item update (in the worst case)
* 1 items for slack space if we need do truncation
* 1 item for free space object
* 3 items for pre-allocation
*/
trans->bytes_reserved = btrfs_calc_trans_metadata_size(root, 10);
ret = btrfs_block_rsv_add(root, trans->block_rsv,
trans->bytes_reserved,
BTRFS_RESERVE_NO_FLUSH);
if (ret)
goto out;
trace_btrfs_space_reservation(root->fs_info, "ino_cache",
trans->transid, trans->bytes_reserved, 1);
again:
inode = lookup_free_ino_inode(root, path);
if (IS_ERR(inode) && (PTR_ERR(inode) != -ENOENT || retry)) {
ret = PTR_ERR(inode);
goto out_release;
}
if (IS_ERR(inode)) {
BUG_ON(retry); /* Logic error */
retry = true;
ret = create_free_ino_inode(root, trans, path);
if (ret)
goto out_release;
goto again;
}
BTRFS_I(inode)->generation = 0;
ret = btrfs_update_inode(trans, root, inode);
if (ret) {
btrfs_abort_transaction(trans, root, ret);
goto out_put;
}
if (i_size_read(inode) > 0) {
ret = btrfs_truncate_free_space_cache(root, trans, NULL, inode);
if (ret) {
if (ret != -ENOSPC)
btrfs_abort_transaction(trans, root, ret);
goto out_put;
}
}
spin_lock(&root->ino_cache_lock);
if (root->ino_cache_state != BTRFS_CACHE_FINISHED) {
ret = -1;
spin_unlock(&root->ino_cache_lock);
goto out_put;
}
spin_unlock(&root->ino_cache_lock);
spin_lock(&ctl->tree_lock);
prealloc = sizeof(struct btrfs_free_space) * ctl->free_extents;
prealloc = ALIGN(prealloc, PAGE_CACHE_SIZE);
prealloc += ctl->total_bitmaps * PAGE_CACHE_SIZE;
spin_unlock(&ctl->tree_lock);
/* Just to make sure we have enough space */
prealloc += 8 * PAGE_CACHE_SIZE;
ret = btrfs_delalloc_reserve_space(inode, prealloc);
if (ret)
goto out_put;
ret = btrfs_prealloc_file_range_trans(inode, trans, 0, 0, prealloc,
prealloc, prealloc, &alloc_hint);
if (ret) {
btrfs_delalloc_release_space(inode, prealloc);
goto out_put;
}
btrfs_free_reserved_data_space(inode, prealloc);
ret = btrfs_write_out_ino_cache(root, trans, path, inode);
out_put:
iput(inode);
out_release:
trace_btrfs_space_reservation(root->fs_info, "ino_cache",
trans->transid, trans->bytes_reserved, 0);
btrfs_block_rsv_release(root, trans->block_rsv, trans->bytes_reserved);
out:
trans->block_rsv = rsv;
trans->bytes_reserved = num_bytes;
btrfs_free_path(path);
return ret;
}
static int btrfs_find_highest_objectid(struct btrfs_root *root, u64 *objectid)
{
struct btrfs_path *path;
int ret;
struct extent_buffer *l;
struct btrfs_key search_key;
struct btrfs_key found_key;
int slot;
path = btrfs_alloc_path();
if (!path)
return -ENOMEM;
search_key.objectid = BTRFS_LAST_FREE_OBJECTID;
search_key.type = -1;
search_key.offset = (u64)-1;
ret = btrfs_search_slot(NULL, root, &search_key, path, 0, 0);
if (ret < 0)
goto error;
BUG_ON(ret == 0); /* Corruption */
if (path->slots[0] > 0) {
slot = path->slots[0] - 1;
l = path->nodes[0];
btrfs_item_key_to_cpu(l, &found_key, slot);
*objectid = max_t(u64, found_key.objectid,
BTRFS_FIRST_FREE_OBJECTID - 1);
} else {
*objectid = BTRFS_FIRST_FREE_OBJECTID - 1;
}
ret = 0;
error:
btrfs_free_path(path);
return ret;
}
int btrfs_find_free_objectid(struct btrfs_root *root, u64 *objectid)
{
int ret;
mutex_lock(&root->objectid_mutex);
if (unlikely(root->highest_objectid < BTRFS_FIRST_FREE_OBJECTID)) {
ret = btrfs_find_highest_objectid(root,
&root->highest_objectid);
if (ret)
goto out;
}
if (unlikely(root->highest_objectid >= BTRFS_LAST_FREE_OBJECTID)) {
ret = -ENOSPC;
goto out;
}
*objectid = ++root->highest_objectid;
ret = 0;
out:
mutex_unlock(&root->objectid_mutex);
return ret;
}