linux/fs/overlayfs/util.c

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// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright (C) 2011 Novell Inc.
* Copyright (C) 2016 Red Hat, Inc.
*/
#include <linux/fs.h>
#include <linux/mount.h>
#include <linux/slab.h>
#include <linux/cred.h>
#include <linux/xattr.h>
#include <linux/exportfs.h>
#include <linux/uuid.h>
#include <linux/namei.h>
#include <linux/ratelimit.h>
#include "overlayfs.h"
int ovl_want_write(struct dentry *dentry)
{
struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
return mnt_want_write(ofs->upper_mnt);
}
void ovl_drop_write(struct dentry *dentry)
{
struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
mnt_drop_write(ofs->upper_mnt);
}
struct dentry *ovl_workdir(struct dentry *dentry)
{
struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
return ofs->workdir;
}
const struct cred *ovl_override_creds(struct super_block *sb)
{
struct ovl_fs *ofs = sb->s_fs_info;
return override_creds(ofs->creator_cred);
}
/*
* Check if underlying fs supports file handles and try to determine encoding
* type, in order to deduce maximum inode number used by fs.
*
* Return 0 if file handles are not supported.
* Return 1 (FILEID_INO32_GEN) if fs uses the default 32bit inode encoding.
* Return -1 if fs uses a non default encoding with unknown inode size.
*/
int ovl_can_decode_fh(struct super_block *sb)
{
if (!sb->s_export_op || !sb->s_export_op->fh_to_dentry)
return 0;
return sb->s_export_op->encode_fh ? -1 : FILEID_INO32_GEN;
}
struct dentry *ovl_indexdir(struct super_block *sb)
{
struct ovl_fs *ofs = sb->s_fs_info;
return ofs->indexdir;
}
/* Index all files on copy up. For now only enabled for NFS export */
bool ovl_index_all(struct super_block *sb)
{
struct ovl_fs *ofs = sb->s_fs_info;
return ofs->config.nfs_export && ofs->config.index;
}
/* Verify lower origin on lookup. For now only enabled for NFS export */
bool ovl_verify_lower(struct super_block *sb)
{
struct ovl_fs *ofs = sb->s_fs_info;
return ofs->config.nfs_export && ofs->config.index;
}
struct ovl_entry *ovl_alloc_entry(unsigned int numlower)
{
size_t size = offsetof(struct ovl_entry, lowerstack[numlower]);
struct ovl_entry *oe = kzalloc(size, GFP_KERNEL);
if (oe)
oe->numlower = numlower;
return oe;
}
bool ovl_dentry_remote(struct dentry *dentry)
{
return dentry->d_flags &
(DCACHE_OP_REVALIDATE | DCACHE_OP_WEAK_REVALIDATE);
}
void ovl_dentry_update_reval(struct dentry *dentry, struct dentry *upperdentry,
unsigned int mask)
{
struct ovl_entry *oe = OVL_E(dentry);
unsigned int i, flags = 0;
for (i = 0; i < oe->numlower; i++)
flags |= oe->lowerstack[i].dentry->d_flags;
spin_lock(&dentry->d_lock);
dentry->d_flags &= ~mask;
dentry->d_flags |= flags & mask;
spin_unlock(&dentry->d_lock);
}
bool ovl_dentry_weird(struct dentry *dentry)
{
return dentry->d_flags & (DCACHE_NEED_AUTOMOUNT |
DCACHE_MANAGE_TRANSIT |
DCACHE_OP_HASH |
DCACHE_OP_COMPARE);
}
enum ovl_path_type ovl_path_type(struct dentry *dentry)
{
struct ovl_entry *oe = dentry->d_fsdata;
enum ovl_path_type type = 0;
if (ovl_dentry_upper(dentry)) {
type = __OVL_PATH_UPPER;
/*
* Non-dir dentry can hold lower dentry of its copy up origin.
*/
if (oe->numlower) {
if (ovl_test_flag(OVL_CONST_INO, d_inode(dentry)))
type |= __OVL_PATH_ORIGIN;
if (d_is_dir(dentry) ||
!ovl_has_upperdata(d_inode(dentry)))
type |= __OVL_PATH_MERGE;
}
} else {
if (oe->numlower > 1)
type |= __OVL_PATH_MERGE;
}
return type;
}
void ovl_path_upper(struct dentry *dentry, struct path *path)
{
struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
path->mnt = ofs->upper_mnt;
path->dentry = ovl_dentry_upper(dentry);
}
void ovl_path_lower(struct dentry *dentry, struct path *path)
{
struct ovl_entry *oe = dentry->d_fsdata;
if (oe->numlower) {
path->mnt = oe->lowerstack[0].layer->mnt;
path->dentry = oe->lowerstack[0].dentry;
} else {
*path = (struct path) { };
}
}
void ovl_path_lowerdata(struct dentry *dentry, struct path *path)
{
struct ovl_entry *oe = dentry->d_fsdata;
if (oe->numlower) {
path->mnt = oe->lowerstack[oe->numlower - 1].layer->mnt;
path->dentry = oe->lowerstack[oe->numlower - 1].dentry;
} else {
*path = (struct path) { };
}
}
enum ovl_path_type ovl_path_real(struct dentry *dentry, struct path *path)
{
enum ovl_path_type type = ovl_path_type(dentry);
if (!OVL_TYPE_UPPER(type))
ovl_path_lower(dentry, path);
else
ovl_path_upper(dentry, path);
return type;
}
struct dentry *ovl_dentry_upper(struct dentry *dentry)
{
return ovl_upperdentry_dereference(OVL_I(d_inode(dentry)));
}
struct dentry *ovl_dentry_lower(struct dentry *dentry)
{
struct ovl_entry *oe = dentry->d_fsdata;
return oe->numlower ? oe->lowerstack[0].dentry : NULL;
}
const struct ovl_layer *ovl_layer_lower(struct dentry *dentry)
{
struct ovl_entry *oe = dentry->d_fsdata;
return oe->numlower ? oe->lowerstack[0].layer : NULL;
}
/*
* ovl_dentry_lower() could return either a data dentry or metacopy dentry
* dependig on what is stored in lowerstack[0]. At times we need to find
* lower dentry which has data (and not metacopy dentry). This helper
* returns the lower data dentry.
*/
struct dentry *ovl_dentry_lowerdata(struct dentry *dentry)
{
struct ovl_entry *oe = dentry->d_fsdata;
return oe->numlower ? oe->lowerstack[oe->numlower - 1].dentry : NULL;
}
struct dentry *ovl_dentry_real(struct dentry *dentry)
{
return ovl_dentry_upper(dentry) ?: ovl_dentry_lower(dentry);
}
struct dentry *ovl_i_dentry_upper(struct inode *inode)
{
return ovl_upperdentry_dereference(OVL_I(inode));
}
struct inode *ovl_inode_upper(struct inode *inode)
{
struct dentry *upperdentry = ovl_i_dentry_upper(inode);
return upperdentry ? d_inode(upperdentry) : NULL;
}
struct inode *ovl_inode_lower(struct inode *inode)
{
return OVL_I(inode)->lower;
}
struct inode *ovl_inode_real(struct inode *inode)
{
return ovl_inode_upper(inode) ?: ovl_inode_lower(inode);
}
/* Return inode which contains lower data. Do not return metacopy */
struct inode *ovl_inode_lowerdata(struct inode *inode)
{
if (WARN_ON(!S_ISREG(inode->i_mode)))
return NULL;
return OVL_I(inode)->lowerdata ?: ovl_inode_lower(inode);
}
/* Return real inode which contains data. Does not return metacopy inode */
struct inode *ovl_inode_realdata(struct inode *inode)
{
struct inode *upperinode;
upperinode = ovl_inode_upper(inode);
if (upperinode && ovl_has_upperdata(inode))
return upperinode;
return ovl_inode_lowerdata(inode);
}
struct ovl_dir_cache *ovl_dir_cache(struct inode *inode)
{
return OVL_I(inode)->cache;
}
void ovl_set_dir_cache(struct inode *inode, struct ovl_dir_cache *cache)
{
OVL_I(inode)->cache = cache;
}
void ovl_dentry_set_flag(unsigned long flag, struct dentry *dentry)
{
set_bit(flag, &OVL_E(dentry)->flags);
}
void ovl_dentry_clear_flag(unsigned long flag, struct dentry *dentry)
{
clear_bit(flag, &OVL_E(dentry)->flags);
}
bool ovl_dentry_test_flag(unsigned long flag, struct dentry *dentry)
{
return test_bit(flag, &OVL_E(dentry)->flags);
}
bool ovl_dentry_is_opaque(struct dentry *dentry)
{
return ovl_dentry_test_flag(OVL_E_OPAQUE, dentry);
}
bool ovl_dentry_is_whiteout(struct dentry *dentry)
{
return !dentry->d_inode && ovl_dentry_is_opaque(dentry);
}
void ovl_dentry_set_opaque(struct dentry *dentry)
{
ovl_dentry_set_flag(OVL_E_OPAQUE, dentry);
}
/*
* For hard links and decoded file handles, it's possible for ovl_dentry_upper()
* to return positive, while there's no actual upper alias for the inode.
* Copy up code needs to know about the existence of the upper alias, so it
* can't use ovl_dentry_upper().
*/
bool ovl_dentry_has_upper_alias(struct dentry *dentry)
{
return ovl_dentry_test_flag(OVL_E_UPPER_ALIAS, dentry);
}
void ovl_dentry_set_upper_alias(struct dentry *dentry)
{
ovl_dentry_set_flag(OVL_E_UPPER_ALIAS, dentry);
}
ovl: A new xattr OVL_XATTR_METACOPY for file on upper Now we will have the capability to have upper inodes which might be only metadata copy up and data is still on lower inode. So add a new xattr OVL_XATTR_METACOPY to distinguish between two cases. Presence of OVL_XATTR_METACOPY reflects that file has been copied up metadata only and and data will be copied up later from lower origin. So this xattr is set when a metadata copy takes place and cleared when data copy takes place. We also use a bit in ovl_inode->flags to cache OVL_UPPERDATA which reflects whether ovl inode has data or not (as opposed to metadata only copy up). If a file is copied up metadata only and later when same file is opened for WRITE, then data copy up takes place. We copy up data, remove METACOPY xattr and then set the UPPERDATA flag in ovl_inode->flags. While all these operations happen with oi->lock held, read side of oi->flags can be lockless. That is another thread on another cpu can check if UPPERDATA flag is set or not. So this gives us an ordering requirement w.r.t UPPERDATA flag. That is, if another cpu sees UPPERDATA flag set, then it should be guaranteed that effects of data copy up and remove xattr operations are also visible. For example. CPU1 CPU2 ovl_open() acquire(oi->lock) ovl_open_maybe_copy_up() ovl_copy_up_data() open_open_need_copy_up() vfs_removexattr() ovl_already_copied_up() ovl_dentry_needs_data_copy_up() ovl_set_flag(OVL_UPPERDATA) ovl_test_flag(OVL_UPPERDATA) release(oi->lock) Say CPU2 is copying up data and in the end sets UPPERDATA flag. But if CPU1 perceives the effects of setting UPPERDATA flag but not the effects of preceding operations (ex. upper that is not fully copied up), it will be a problem. Hence this patch introduces smp_wmb() on setting UPPERDATA flag operation and smp_rmb() on UPPERDATA flag test operation. May be some other lock or barrier is already covering it. But I am not sure what that is and is it obvious enough that we will not break it in future. So hence trying to be safe here and introducing barriers explicitly for UPPERDATA flag/bit. Signed-off-by: Vivek Goyal <vgoyal@redhat.com> Reviewed-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-05-11 15:49:28 +00:00
static bool ovl_should_check_upperdata(struct inode *inode)
{
if (!S_ISREG(inode->i_mode))
return false;
if (!ovl_inode_lower(inode))
return false;
return true;
}
bool ovl_has_upperdata(struct inode *inode)
{
if (!ovl_should_check_upperdata(inode))
return true;
if (!ovl_test_flag(OVL_UPPERDATA, inode))
return false;
/*
* Pairs with smp_wmb() in ovl_set_upperdata(). Main user of
* ovl_has_upperdata() is ovl_copy_up_meta_inode_data(). Make sure
* if setting of OVL_UPPERDATA is visible, then effects of writes
* before that are visible too.
*/
smp_rmb();
return true;
}
void ovl_set_upperdata(struct inode *inode)
{
/*
* Pairs with smp_rmb() in ovl_has_upperdata(). Make sure
* if OVL_UPPERDATA flag is visible, then effects of write operations
* before it are visible as well.
*/
smp_wmb();
ovl_set_flag(OVL_UPPERDATA, inode);
}
/* Caller should hold ovl_inode->lock */
bool ovl_dentry_needs_data_copy_up_locked(struct dentry *dentry, int flags)
{
if (!ovl_open_flags_need_copy_up(flags))
return false;
return !ovl_test_flag(OVL_UPPERDATA, d_inode(dentry));
}
bool ovl_dentry_needs_data_copy_up(struct dentry *dentry, int flags)
{
if (!ovl_open_flags_need_copy_up(flags))
return false;
return !ovl_has_upperdata(d_inode(dentry));
}
bool ovl_redirect_dir(struct super_block *sb)
{
struct ovl_fs *ofs = sb->s_fs_info;
return ofs->config.redirect_dir && !ofs->noxattr;
}
const char *ovl_dentry_get_redirect(struct dentry *dentry)
{
return OVL_I(d_inode(dentry))->redirect;
}
void ovl_dentry_set_redirect(struct dentry *dentry, const char *redirect)
{
struct ovl_inode *oi = OVL_I(d_inode(dentry));
kfree(oi->redirect);
oi->redirect = redirect;
}
void ovl_inode_update(struct inode *inode, struct dentry *upperdentry)
{
struct inode *upperinode = d_inode(upperdentry);
WARN_ON(OVL_I(inode)->__upperdentry);
/*
* Make sure upperdentry is consistent before making it visible
*/
smp_wmb();
OVL_I(inode)->__upperdentry = upperdentry;
if (inode_unhashed(inode)) {
inode->i_private = upperinode;
__insert_inode_hash(inode, (unsigned long) upperinode);
}
}
static void ovl_dentry_version_inc(struct dentry *dentry, bool impurity)
{
struct inode *inode = d_inode(dentry);
WARN_ON(!inode_is_locked(inode));
/*
* Version is used by readdir code to keep cache consistent. For merge
* dirs all changes need to be noted. For non-merge dirs, cache only
* contains impure (ones which have been copied up and have origins)
* entries, so only need to note changes to impure entries.
*/
if (OVL_TYPE_MERGE(ovl_path_type(dentry)) || impurity)
OVL_I(inode)->version++;
}
void ovl_dir_modified(struct dentry *dentry, bool impurity)
{
/* Copy mtime/ctime */
ovl_copyattr(d_inode(ovl_dentry_upper(dentry)), d_inode(dentry));
ovl_dentry_version_inc(dentry, impurity);
}
u64 ovl_dentry_version_get(struct dentry *dentry)
{
struct inode *inode = d_inode(dentry);
WARN_ON(!inode_is_locked(inode));
return OVL_I(inode)->version;
}
bool ovl_is_whiteout(struct dentry *dentry)
{
struct inode *inode = dentry->d_inode;
return inode && IS_WHITEOUT(inode);
}
struct file *ovl_path_open(struct path *path, int flags)
{
return dentry_open(path, flags | O_NOATIME, current_cred());
}
ovl: A new xattr OVL_XATTR_METACOPY for file on upper Now we will have the capability to have upper inodes which might be only metadata copy up and data is still on lower inode. So add a new xattr OVL_XATTR_METACOPY to distinguish between two cases. Presence of OVL_XATTR_METACOPY reflects that file has been copied up metadata only and and data will be copied up later from lower origin. So this xattr is set when a metadata copy takes place and cleared when data copy takes place. We also use a bit in ovl_inode->flags to cache OVL_UPPERDATA which reflects whether ovl inode has data or not (as opposed to metadata only copy up). If a file is copied up metadata only and later when same file is opened for WRITE, then data copy up takes place. We copy up data, remove METACOPY xattr and then set the UPPERDATA flag in ovl_inode->flags. While all these operations happen with oi->lock held, read side of oi->flags can be lockless. That is another thread on another cpu can check if UPPERDATA flag is set or not. So this gives us an ordering requirement w.r.t UPPERDATA flag. That is, if another cpu sees UPPERDATA flag set, then it should be guaranteed that effects of data copy up and remove xattr operations are also visible. For example. CPU1 CPU2 ovl_open() acquire(oi->lock) ovl_open_maybe_copy_up() ovl_copy_up_data() open_open_need_copy_up() vfs_removexattr() ovl_already_copied_up() ovl_dentry_needs_data_copy_up() ovl_set_flag(OVL_UPPERDATA) ovl_test_flag(OVL_UPPERDATA) release(oi->lock) Say CPU2 is copying up data and in the end sets UPPERDATA flag. But if CPU1 perceives the effects of setting UPPERDATA flag but not the effects of preceding operations (ex. upper that is not fully copied up), it will be a problem. Hence this patch introduces smp_wmb() on setting UPPERDATA flag operation and smp_rmb() on UPPERDATA flag test operation. May be some other lock or barrier is already covering it. But I am not sure what that is and is it obvious enough that we will not break it in future. So hence trying to be safe here and introducing barriers explicitly for UPPERDATA flag/bit. Signed-off-by: Vivek Goyal <vgoyal@redhat.com> Reviewed-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-05-11 15:49:28 +00:00
/* Caller should hold ovl_inode->lock */
static bool ovl_already_copied_up_locked(struct dentry *dentry, int flags)
{
bool disconnected = dentry->d_flags & DCACHE_DISCONNECTED;
if (ovl_dentry_upper(dentry) &&
(ovl_dentry_has_upper_alias(dentry) || disconnected) &&
!ovl_dentry_needs_data_copy_up_locked(dentry, flags))
return true;
return false;
}
bool ovl_already_copied_up(struct dentry *dentry, int flags)
{
bool disconnected = dentry->d_flags & DCACHE_DISCONNECTED;
/*
* Check if copy-up has happened as well as for upper alias (in
* case of hard links) is there.
*
* Both checks are lockless:
* - false negatives: will recheck under oi->lock
* - false positives:
* + ovl_dentry_upper() uses memory barriers to ensure the
* upper dentry is up-to-date
* + ovl_dentry_has_upper_alias() relies on locking of
* upper parent i_rwsem to prevent reordering copy-up
* with rename.
*/
if (ovl_dentry_upper(dentry) &&
ovl: A new xattr OVL_XATTR_METACOPY for file on upper Now we will have the capability to have upper inodes which might be only metadata copy up and data is still on lower inode. So add a new xattr OVL_XATTR_METACOPY to distinguish between two cases. Presence of OVL_XATTR_METACOPY reflects that file has been copied up metadata only and and data will be copied up later from lower origin. So this xattr is set when a metadata copy takes place and cleared when data copy takes place. We also use a bit in ovl_inode->flags to cache OVL_UPPERDATA which reflects whether ovl inode has data or not (as opposed to metadata only copy up). If a file is copied up metadata only and later when same file is opened for WRITE, then data copy up takes place. We copy up data, remove METACOPY xattr and then set the UPPERDATA flag in ovl_inode->flags. While all these operations happen with oi->lock held, read side of oi->flags can be lockless. That is another thread on another cpu can check if UPPERDATA flag is set or not. So this gives us an ordering requirement w.r.t UPPERDATA flag. That is, if another cpu sees UPPERDATA flag set, then it should be guaranteed that effects of data copy up and remove xattr operations are also visible. For example. CPU1 CPU2 ovl_open() acquire(oi->lock) ovl_open_maybe_copy_up() ovl_copy_up_data() open_open_need_copy_up() vfs_removexattr() ovl_already_copied_up() ovl_dentry_needs_data_copy_up() ovl_set_flag(OVL_UPPERDATA) ovl_test_flag(OVL_UPPERDATA) release(oi->lock) Say CPU2 is copying up data and in the end sets UPPERDATA flag. But if CPU1 perceives the effects of setting UPPERDATA flag but not the effects of preceding operations (ex. upper that is not fully copied up), it will be a problem. Hence this patch introduces smp_wmb() on setting UPPERDATA flag operation and smp_rmb() on UPPERDATA flag test operation. May be some other lock or barrier is already covering it. But I am not sure what that is and is it obvious enough that we will not break it in future. So hence trying to be safe here and introducing barriers explicitly for UPPERDATA flag/bit. Signed-off-by: Vivek Goyal <vgoyal@redhat.com> Reviewed-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-05-11 15:49:28 +00:00
(ovl_dentry_has_upper_alias(dentry) || disconnected) &&
!ovl_dentry_needs_data_copy_up(dentry, flags))
return true;
return false;
}
ovl: A new xattr OVL_XATTR_METACOPY for file on upper Now we will have the capability to have upper inodes which might be only metadata copy up and data is still on lower inode. So add a new xattr OVL_XATTR_METACOPY to distinguish between two cases. Presence of OVL_XATTR_METACOPY reflects that file has been copied up metadata only and and data will be copied up later from lower origin. So this xattr is set when a metadata copy takes place and cleared when data copy takes place. We also use a bit in ovl_inode->flags to cache OVL_UPPERDATA which reflects whether ovl inode has data or not (as opposed to metadata only copy up). If a file is copied up metadata only and later when same file is opened for WRITE, then data copy up takes place. We copy up data, remove METACOPY xattr and then set the UPPERDATA flag in ovl_inode->flags. While all these operations happen with oi->lock held, read side of oi->flags can be lockless. That is another thread on another cpu can check if UPPERDATA flag is set or not. So this gives us an ordering requirement w.r.t UPPERDATA flag. That is, if another cpu sees UPPERDATA flag set, then it should be guaranteed that effects of data copy up and remove xattr operations are also visible. For example. CPU1 CPU2 ovl_open() acquire(oi->lock) ovl_open_maybe_copy_up() ovl_copy_up_data() open_open_need_copy_up() vfs_removexattr() ovl_already_copied_up() ovl_dentry_needs_data_copy_up() ovl_set_flag(OVL_UPPERDATA) ovl_test_flag(OVL_UPPERDATA) release(oi->lock) Say CPU2 is copying up data and in the end sets UPPERDATA flag. But if CPU1 perceives the effects of setting UPPERDATA flag but not the effects of preceding operations (ex. upper that is not fully copied up), it will be a problem. Hence this patch introduces smp_wmb() on setting UPPERDATA flag operation and smp_rmb() on UPPERDATA flag test operation. May be some other lock or barrier is already covering it. But I am not sure what that is and is it obvious enough that we will not break it in future. So hence trying to be safe here and introducing barriers explicitly for UPPERDATA flag/bit. Signed-off-by: Vivek Goyal <vgoyal@redhat.com> Reviewed-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-05-11 15:49:28 +00:00
int ovl_copy_up_start(struct dentry *dentry, int flags)
{
struct inode *inode = d_inode(dentry);
int err;
err = ovl_inode_lock_interruptible(inode);
ovl: A new xattr OVL_XATTR_METACOPY for file on upper Now we will have the capability to have upper inodes which might be only metadata copy up and data is still on lower inode. So add a new xattr OVL_XATTR_METACOPY to distinguish between two cases. Presence of OVL_XATTR_METACOPY reflects that file has been copied up metadata only and and data will be copied up later from lower origin. So this xattr is set when a metadata copy takes place and cleared when data copy takes place. We also use a bit in ovl_inode->flags to cache OVL_UPPERDATA which reflects whether ovl inode has data or not (as opposed to metadata only copy up). If a file is copied up metadata only and later when same file is opened for WRITE, then data copy up takes place. We copy up data, remove METACOPY xattr and then set the UPPERDATA flag in ovl_inode->flags. While all these operations happen with oi->lock held, read side of oi->flags can be lockless. That is another thread on another cpu can check if UPPERDATA flag is set or not. So this gives us an ordering requirement w.r.t UPPERDATA flag. That is, if another cpu sees UPPERDATA flag set, then it should be guaranteed that effects of data copy up and remove xattr operations are also visible. For example. CPU1 CPU2 ovl_open() acquire(oi->lock) ovl_open_maybe_copy_up() ovl_copy_up_data() open_open_need_copy_up() vfs_removexattr() ovl_already_copied_up() ovl_dentry_needs_data_copy_up() ovl_set_flag(OVL_UPPERDATA) ovl_test_flag(OVL_UPPERDATA) release(oi->lock) Say CPU2 is copying up data and in the end sets UPPERDATA flag. But if CPU1 perceives the effects of setting UPPERDATA flag but not the effects of preceding operations (ex. upper that is not fully copied up), it will be a problem. Hence this patch introduces smp_wmb() on setting UPPERDATA flag operation and smp_rmb() on UPPERDATA flag test operation. May be some other lock or barrier is already covering it. But I am not sure what that is and is it obvious enough that we will not break it in future. So hence trying to be safe here and introducing barriers explicitly for UPPERDATA flag/bit. Signed-off-by: Vivek Goyal <vgoyal@redhat.com> Reviewed-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-05-11 15:49:28 +00:00
if (!err && ovl_already_copied_up_locked(dentry, flags)) {
err = 1; /* Already copied up */
ovl_inode_unlock(inode);
}
return err;
}
void ovl_copy_up_end(struct dentry *dentry)
{
ovl_inode_unlock(d_inode(dentry));
}
bool ovl_check_origin_xattr(struct dentry *dentry)
{
int res;
res = vfs_getxattr(dentry, OVL_XATTR_ORIGIN, NULL, 0);
/* Zero size value means "copied up but origin unknown" */
if (res >= 0)
return true;
return false;
}
bool ovl_check_dir_xattr(struct dentry *dentry, const char *name)
{
int res;
char val;
if (!d_is_dir(dentry))
return false;
res = vfs_getxattr(dentry, name, &val, 1);
if (res == 1 && val == 'y')
return true;
return false;
}
int ovl_check_setxattr(struct dentry *dentry, struct dentry *upperdentry,
const char *name, const void *value, size_t size,
int xerr)
{
int err;
struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
if (ofs->noxattr)
return xerr;
err = ovl_do_setxattr(upperdentry, name, value, size, 0);
if (err == -EOPNOTSUPP) {
pr_warn("cannot set %s xattr on upper\n", name);
ofs->noxattr = true;
return xerr;
}
return err;
}
int ovl_set_impure(struct dentry *dentry, struct dentry *upperdentry)
{
int err;
if (ovl_test_flag(OVL_IMPURE, d_inode(dentry)))
return 0;
/*
* Do not fail when upper doesn't support xattrs.
* Upper inodes won't have origin nor redirect xattr anyway.
*/
err = ovl_check_setxattr(dentry, upperdentry, OVL_XATTR_IMPURE,
"y", 1, 0);
if (!err)
ovl_set_flag(OVL_IMPURE, d_inode(dentry));
return err;
}
void ovl_set_flag(unsigned long flag, struct inode *inode)
{
set_bit(flag, &OVL_I(inode)->flags);
}
void ovl_clear_flag(unsigned long flag, struct inode *inode)
{
clear_bit(flag, &OVL_I(inode)->flags);
}
bool ovl_test_flag(unsigned long flag, struct inode *inode)
{
return test_bit(flag, &OVL_I(inode)->flags);
}
/**
* Caller must hold a reference to inode to prevent it from being freed while
* it is marked inuse.
*/
bool ovl_inuse_trylock(struct dentry *dentry)
{
struct inode *inode = d_inode(dentry);
bool locked = false;
spin_lock(&inode->i_lock);
if (!(inode->i_state & I_OVL_INUSE)) {
inode->i_state |= I_OVL_INUSE;
locked = true;
}
spin_unlock(&inode->i_lock);
return locked;
}
void ovl_inuse_unlock(struct dentry *dentry)
{
if (dentry) {
struct inode *inode = d_inode(dentry);
spin_lock(&inode->i_lock);
WARN_ON(!(inode->i_state & I_OVL_INUSE));
inode->i_state &= ~I_OVL_INUSE;
spin_unlock(&inode->i_lock);
}
}
ovl: detect overlapping layers Overlapping overlay layers are not supported and can cause unexpected behavior, but overlayfs does not currently check or warn about these configurations. User is not supposed to specify the same directory for upper and lower dirs or for different lower layers and user is not supposed to specify directories that are descendants of each other for overlay layers, but that is exactly what this zysbot repro did: https://syzkaller.appspot.com/x/repro.syz?x=12c7a94f400000 Moving layer root directories into other layers while overlayfs is mounted could also result in unexpected behavior. This commit places "traps" in the overlay inode hash table. Those traps are dummy overlay inodes that are hashed by the layers root inodes. On mount, the hash table trap entries are used to verify that overlay layers are not overlapping. While at it, we also verify that overlay layers are not overlapping with directories "in-use" by other overlay instances as upperdir/workdir. On lookup, the trap entries are used to verify that overlay layers root inodes have not been moved into other layers after mount. Some examples: $ ./run --ov --samefs -s ... ( mkdir -p base/upper/0/u base/upper/0/w base/lower lower upper mnt mount -o bind base/lower lower mount -o bind base/upper upper mount -t overlay none mnt ... -o lowerdir=lower,upperdir=upper/0/u,workdir=upper/0/w) $ umount mnt $ mount -t overlay none mnt ... -o lowerdir=base,upperdir=upper/0/u,workdir=upper/0/w [ 94.434900] overlayfs: overlapping upperdir path mount: mount overlay on mnt failed: Too many levels of symbolic links $ mount -t overlay none mnt ... -o lowerdir=upper/0/u,upperdir=upper/0/u,workdir=upper/0/w [ 151.350132] overlayfs: conflicting lowerdir path mount: none is already mounted or mnt busy $ mount -t overlay none mnt ... -o lowerdir=lower:lower/a,upperdir=upper/0/u,workdir=upper/0/w [ 201.205045] overlayfs: overlapping lowerdir path mount: mount overlay on mnt failed: Too many levels of symbolic links $ mount -t overlay none mnt ... -o lowerdir=lower,upperdir=upper/0/u,workdir=upper/0/w $ mv base/upper/0/ base/lower/ $ find mnt/0 mnt/0 mnt/0/w find: 'mnt/0/w/work': Too many levels of symbolic links find: 'mnt/0/u': Too many levels of symbolic links Reported-by: syzbot+9c69c282adc4edd2b540@syzkaller.appspotmail.com Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2019-04-18 14:42:08 +00:00
bool ovl_is_inuse(struct dentry *dentry)
{
struct inode *inode = d_inode(dentry);
bool inuse;
spin_lock(&inode->i_lock);
inuse = (inode->i_state & I_OVL_INUSE);
spin_unlock(&inode->i_lock);
return inuse;
}
/*
* Does this overlay dentry need to be indexed on copy up?
*/
bool ovl_need_index(struct dentry *dentry)
{
struct dentry *lower = ovl_dentry_lower(dentry);
if (!lower || !ovl_indexdir(dentry->d_sb))
return false;
/* Index all files for NFS export and consistency verification */
if (ovl_index_all(dentry->d_sb))
return true;
/* Index only lower hardlinks on copy up */
if (!d_is_dir(lower) && d_inode(lower)->i_nlink > 1)
return true;
return false;
}
/* Caller must hold OVL_I(inode)->lock */
static void ovl_cleanup_index(struct dentry *dentry)
{
struct dentry *indexdir = ovl_indexdir(dentry->d_sb);
struct inode *dir = indexdir->d_inode;
struct dentry *lowerdentry = ovl_dentry_lower(dentry);
struct dentry *upperdentry = ovl_dentry_upper(dentry);
struct dentry *index = NULL;
struct inode *inode;
struct qstr name = { };
int err;
err = ovl_get_index_name(lowerdentry, &name);
if (err)
goto fail;
inode = d_inode(upperdentry);
if (!S_ISDIR(inode->i_mode) && inode->i_nlink != 1) {
pr_warn_ratelimited("cleanup linked index (%pd2, ino=%lu, nlink=%u)\n",
upperdentry, inode->i_ino, inode->i_nlink);
/*
* We either have a bug with persistent union nlink or a lower
* hardlink was added while overlay is mounted. Adding a lower
* hardlink and then unlinking all overlay hardlinks would drop
* overlay nlink to zero before all upper inodes are unlinked.
* As a safety measure, when that situation is detected, set
* the overlay nlink to the index inode nlink minus one for the
* index entry itself.
*/
set_nlink(d_inode(dentry), inode->i_nlink - 1);
ovl_set_nlink_upper(dentry);
goto out;
}
inode_lock_nested(dir, I_MUTEX_PARENT);
index = lookup_one_len(name.name, indexdir, name.len);
err = PTR_ERR(index);
if (IS_ERR(index)) {
index = NULL;
} else if (ovl_index_all(dentry->d_sb)) {
/* Whiteout orphan index to block future open by handle */
err = ovl_cleanup_and_whiteout(indexdir, dir, index);
} else {
/* Cleanup orphan index entries */
err = ovl_cleanup(dir, index);
}
inode_unlock(dir);
if (err)
goto fail;
out:
kfree(name.name);
dput(index);
return;
fail:
pr_err("cleanup index of '%pd2' failed (%i)\n", dentry, err);
goto out;
}
/*
* Operations that change overlay inode and upper inode nlink need to be
* synchronized with copy up for persistent nlink accounting.
*/
int ovl_nlink_start(struct dentry *dentry)
{
struct inode *inode = d_inode(dentry);
const struct cred *old_cred;
int err;
if (WARN_ON(!inode))
return -ENOENT;
/*
* With inodes index is enabled, we store the union overlay nlink
* in an xattr on the index inode. When whiting out an indexed lower,
* we need to decrement the overlay persistent nlink, but before the
* first copy up, we have no upper index inode to store the xattr.
*
* As a workaround, before whiteout/rename over an indexed lower,
* copy up to create the upper index. Creating the upper index will
* initialize the overlay nlink, so it could be dropped if unlink
* or rename succeeds.
*
* TODO: implement metadata only index copy up when called with
* ovl_copy_up_flags(dentry, O_PATH).
*/
if (ovl_need_index(dentry) && !ovl_dentry_has_upper_alias(dentry)) {
err = ovl_copy_up(dentry);
if (err)
return err;
}
err = ovl_inode_lock_interruptible(inode);
if (err)
return err;
if (d_is_dir(dentry) || !ovl_test_flag(OVL_INDEX, inode))
goto out;
old_cred = ovl_override_creds(dentry->d_sb);
/*
* The overlay inode nlink should be incremented/decremented IFF the
* upper operation succeeds, along with nlink change of upper inode.
* Therefore, before link/unlink/rename, we store the union nlink
* value relative to the upper inode nlink in an upper inode xattr.
*/
err = ovl_set_nlink_upper(dentry);
revert_creds(old_cred);
out:
if (err)
ovl_inode_unlock(inode);
return err;
}
void ovl_nlink_end(struct dentry *dentry)
{
struct inode *inode = d_inode(dentry);
if (ovl_test_flag(OVL_INDEX, inode) && inode->i_nlink == 0) {
const struct cred *old_cred;
old_cred = ovl_override_creds(dentry->d_sb);
ovl_cleanup_index(dentry);
revert_creds(old_cred);
}
ovl_inode_unlock(inode);
}
int ovl_lock_rename_workdir(struct dentry *workdir, struct dentry *upperdir)
{
/* Workdir should not be the same as upperdir */
if (workdir == upperdir)
goto err;
/* Workdir should not be subdir of upperdir and vice versa */
if (lock_rename(workdir, upperdir) != NULL)
goto err_unlock;
return 0;
err_unlock:
unlock_rename(workdir, upperdir);
err:
pr_err("failed to lock workdir+upperdir\n");
return -EIO;
}
/* err < 0, 0 if no metacopy xattr, 1 if metacopy xattr found */
int ovl_check_metacopy_xattr(struct dentry *dentry)
{
int res;
/* Only regular files can have metacopy xattr */
if (!S_ISREG(d_inode(dentry)->i_mode))
return 0;
res = vfs_getxattr(dentry, OVL_XATTR_METACOPY, NULL, 0);
if (res < 0) {
if (res == -ENODATA || res == -EOPNOTSUPP)
return 0;
goto out;
}
return 1;
out:
pr_warn_ratelimited("failed to get metacopy (%i)\n", res);
return res;
}
bool ovl_is_metacopy_dentry(struct dentry *dentry)
{
struct ovl_entry *oe = dentry->d_fsdata;
if (!d_is_reg(dentry))
return false;
if (ovl_dentry_upper(dentry)) {
if (!ovl_has_upperdata(d_inode(dentry)))
return true;
return false;
}
return (oe->numlower > 1);
}
ovl: Check redirect on index as well Right now we seem to check redirect only if upperdentry is found. But it is possible that there is no upperdentry but later we found an index. We need to check redirect on index as well and set it in ovl_inode->redirect. Otherwise link code can assume that dentry does not have redirect and place a new one which breaks things. In my testing overlay/033 test started failing in xfstests. Following are the details. For example do following. $ mkdir lower upper work merged - Make lower dir with 4 links. $ echo "foo" > lower/l0.txt $ ln lower/l0.txt lower/l1.txt $ ln lower/l0.txt lower/l2.txt $ ln lower/l0.txt lower/l3.txt - Mount with index on and metacopy on. $ mount -t overlay -o lowerdir=lower,upperdir=upper,workdir=work,\ index=on,metacopy=on none merged - Link lower $ ln merged/l0.txt merged/l4.txt (This will metadata copy up of l0.txt and put an absolute redirect /l0.txt) $ echo 2 > /proc/sys/vm/drop/caches $ ls merged/l1.txt (Now l1.txt will be looked up. There is no upper dentry but there is lower dentry and index will be found. We don't check for redirect on index, hence ovl_inode->redirect will be NULL.) - Link Upper $ ln merged/l4.txt merged/l5.txt (Lookup of l4.txt will use inode from l1.txt lookup which is still in cache. It has ovl_inode->redirect NULL, hence link will put a new redirect and replace /l0.txt with /l4.txt - Drop caches. echo 2 > /proc/sys/vm/drop_caches - List l1.txt and it returns -ESTALE $ ls merged/l0.txt (It returns stale because, we found a metacopy of l0.txt in upper and it has redirect l4.txt but there is no file named l4.txt in lower layer. So lower data copy is not found and -ESTALE is returned.) So problem here is that we did not process redirect on index. Check redirect on index as well and then problem is fixed. Signed-off-by: Vivek Goyal <vgoyal@redhat.com> Reviewed-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-05-11 15:49:32 +00:00
ssize_t ovl_getxattr(struct dentry *dentry, char *name, char **value,
size_t padding)
ovl: Check redirect on index as well Right now we seem to check redirect only if upperdentry is found. But it is possible that there is no upperdentry but later we found an index. We need to check redirect on index as well and set it in ovl_inode->redirect. Otherwise link code can assume that dentry does not have redirect and place a new one which breaks things. In my testing overlay/033 test started failing in xfstests. Following are the details. For example do following. $ mkdir lower upper work merged - Make lower dir with 4 links. $ echo "foo" > lower/l0.txt $ ln lower/l0.txt lower/l1.txt $ ln lower/l0.txt lower/l2.txt $ ln lower/l0.txt lower/l3.txt - Mount with index on and metacopy on. $ mount -t overlay -o lowerdir=lower,upperdir=upper,workdir=work,\ index=on,metacopy=on none merged - Link lower $ ln merged/l0.txt merged/l4.txt (This will metadata copy up of l0.txt and put an absolute redirect /l0.txt) $ echo 2 > /proc/sys/vm/drop/caches $ ls merged/l1.txt (Now l1.txt will be looked up. There is no upper dentry but there is lower dentry and index will be found. We don't check for redirect on index, hence ovl_inode->redirect will be NULL.) - Link Upper $ ln merged/l4.txt merged/l5.txt (Lookup of l4.txt will use inode from l1.txt lookup which is still in cache. It has ovl_inode->redirect NULL, hence link will put a new redirect and replace /l0.txt with /l4.txt - Drop caches. echo 2 > /proc/sys/vm/drop_caches - List l1.txt and it returns -ESTALE $ ls merged/l0.txt (It returns stale because, we found a metacopy of l0.txt in upper and it has redirect l4.txt but there is no file named l4.txt in lower layer. So lower data copy is not found and -ESTALE is returned.) So problem here is that we did not process redirect on index. Check redirect on index as well and then problem is fixed. Signed-off-by: Vivek Goyal <vgoyal@redhat.com> Reviewed-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-05-11 15:49:32 +00:00
{
ssize_t res;
char *buf = NULL;
ovl: Check redirect on index as well Right now we seem to check redirect only if upperdentry is found. But it is possible that there is no upperdentry but later we found an index. We need to check redirect on index as well and set it in ovl_inode->redirect. Otherwise link code can assume that dentry does not have redirect and place a new one which breaks things. In my testing overlay/033 test started failing in xfstests. Following are the details. For example do following. $ mkdir lower upper work merged - Make lower dir with 4 links. $ echo "foo" > lower/l0.txt $ ln lower/l0.txt lower/l1.txt $ ln lower/l0.txt lower/l2.txt $ ln lower/l0.txt lower/l3.txt - Mount with index on and metacopy on. $ mount -t overlay -o lowerdir=lower,upperdir=upper,workdir=work,\ index=on,metacopy=on none merged - Link lower $ ln merged/l0.txt merged/l4.txt (This will metadata copy up of l0.txt and put an absolute redirect /l0.txt) $ echo 2 > /proc/sys/vm/drop/caches $ ls merged/l1.txt (Now l1.txt will be looked up. There is no upper dentry but there is lower dentry and index will be found. We don't check for redirect on index, hence ovl_inode->redirect will be NULL.) - Link Upper $ ln merged/l4.txt merged/l5.txt (Lookup of l4.txt will use inode from l1.txt lookup which is still in cache. It has ovl_inode->redirect NULL, hence link will put a new redirect and replace /l0.txt with /l4.txt - Drop caches. echo 2 > /proc/sys/vm/drop_caches - List l1.txt and it returns -ESTALE $ ls merged/l0.txt (It returns stale because, we found a metacopy of l0.txt in upper and it has redirect l4.txt but there is no file named l4.txt in lower layer. So lower data copy is not found and -ESTALE is returned.) So problem here is that we did not process redirect on index. Check redirect on index as well and then problem is fixed. Signed-off-by: Vivek Goyal <vgoyal@redhat.com> Reviewed-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-05-11 15:49:32 +00:00
res = vfs_getxattr(dentry, name, NULL, 0);
ovl: Check redirect on index as well Right now we seem to check redirect only if upperdentry is found. But it is possible that there is no upperdentry but later we found an index. We need to check redirect on index as well and set it in ovl_inode->redirect. Otherwise link code can assume that dentry does not have redirect and place a new one which breaks things. In my testing overlay/033 test started failing in xfstests. Following are the details. For example do following. $ mkdir lower upper work merged - Make lower dir with 4 links. $ echo "foo" > lower/l0.txt $ ln lower/l0.txt lower/l1.txt $ ln lower/l0.txt lower/l2.txt $ ln lower/l0.txt lower/l3.txt - Mount with index on and metacopy on. $ mount -t overlay -o lowerdir=lower,upperdir=upper,workdir=work,\ index=on,metacopy=on none merged - Link lower $ ln merged/l0.txt merged/l4.txt (This will metadata copy up of l0.txt and put an absolute redirect /l0.txt) $ echo 2 > /proc/sys/vm/drop/caches $ ls merged/l1.txt (Now l1.txt will be looked up. There is no upper dentry but there is lower dentry and index will be found. We don't check for redirect on index, hence ovl_inode->redirect will be NULL.) - Link Upper $ ln merged/l4.txt merged/l5.txt (Lookup of l4.txt will use inode from l1.txt lookup which is still in cache. It has ovl_inode->redirect NULL, hence link will put a new redirect and replace /l0.txt with /l4.txt - Drop caches. echo 2 > /proc/sys/vm/drop_caches - List l1.txt and it returns -ESTALE $ ls merged/l0.txt (It returns stale because, we found a metacopy of l0.txt in upper and it has redirect l4.txt but there is no file named l4.txt in lower layer. So lower data copy is not found and -ESTALE is returned.) So problem here is that we did not process redirect on index. Check redirect on index as well and then problem is fixed. Signed-off-by: Vivek Goyal <vgoyal@redhat.com> Reviewed-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-05-11 15:49:32 +00:00
if (res < 0) {
if (res == -ENODATA || res == -EOPNOTSUPP)
return -ENODATA;
ovl: Check redirect on index as well Right now we seem to check redirect only if upperdentry is found. But it is possible that there is no upperdentry but later we found an index. We need to check redirect on index as well and set it in ovl_inode->redirect. Otherwise link code can assume that dentry does not have redirect and place a new one which breaks things. In my testing overlay/033 test started failing in xfstests. Following are the details. For example do following. $ mkdir lower upper work merged - Make lower dir with 4 links. $ echo "foo" > lower/l0.txt $ ln lower/l0.txt lower/l1.txt $ ln lower/l0.txt lower/l2.txt $ ln lower/l0.txt lower/l3.txt - Mount with index on and metacopy on. $ mount -t overlay -o lowerdir=lower,upperdir=upper,workdir=work,\ index=on,metacopy=on none merged - Link lower $ ln merged/l0.txt merged/l4.txt (This will metadata copy up of l0.txt and put an absolute redirect /l0.txt) $ echo 2 > /proc/sys/vm/drop/caches $ ls merged/l1.txt (Now l1.txt will be looked up. There is no upper dentry but there is lower dentry and index will be found. We don't check for redirect on index, hence ovl_inode->redirect will be NULL.) - Link Upper $ ln merged/l4.txt merged/l5.txt (Lookup of l4.txt will use inode from l1.txt lookup which is still in cache. It has ovl_inode->redirect NULL, hence link will put a new redirect and replace /l0.txt with /l4.txt - Drop caches. echo 2 > /proc/sys/vm/drop_caches - List l1.txt and it returns -ESTALE $ ls merged/l0.txt (It returns stale because, we found a metacopy of l0.txt in upper and it has redirect l4.txt but there is no file named l4.txt in lower layer. So lower data copy is not found and -ESTALE is returned.) So problem here is that we did not process redirect on index. Check redirect on index as well and then problem is fixed. Signed-off-by: Vivek Goyal <vgoyal@redhat.com> Reviewed-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-05-11 15:49:32 +00:00
goto fail;
}
if (res != 0) {
buf = kzalloc(res + padding, GFP_KERNEL);
if (!buf)
return -ENOMEM;
ovl: Check redirect on index as well Right now we seem to check redirect only if upperdentry is found. But it is possible that there is no upperdentry but later we found an index. We need to check redirect on index as well and set it in ovl_inode->redirect. Otherwise link code can assume that dentry does not have redirect and place a new one which breaks things. In my testing overlay/033 test started failing in xfstests. Following are the details. For example do following. $ mkdir lower upper work merged - Make lower dir with 4 links. $ echo "foo" > lower/l0.txt $ ln lower/l0.txt lower/l1.txt $ ln lower/l0.txt lower/l2.txt $ ln lower/l0.txt lower/l3.txt - Mount with index on and metacopy on. $ mount -t overlay -o lowerdir=lower,upperdir=upper,workdir=work,\ index=on,metacopy=on none merged - Link lower $ ln merged/l0.txt merged/l4.txt (This will metadata copy up of l0.txt and put an absolute redirect /l0.txt) $ echo 2 > /proc/sys/vm/drop/caches $ ls merged/l1.txt (Now l1.txt will be looked up. There is no upper dentry but there is lower dentry and index will be found. We don't check for redirect on index, hence ovl_inode->redirect will be NULL.) - Link Upper $ ln merged/l4.txt merged/l5.txt (Lookup of l4.txt will use inode from l1.txt lookup which is still in cache. It has ovl_inode->redirect NULL, hence link will put a new redirect and replace /l0.txt with /l4.txt - Drop caches. echo 2 > /proc/sys/vm/drop_caches - List l1.txt and it returns -ESTALE $ ls merged/l0.txt (It returns stale because, we found a metacopy of l0.txt in upper and it has redirect l4.txt but there is no file named l4.txt in lower layer. So lower data copy is not found and -ESTALE is returned.) So problem here is that we did not process redirect on index. Check redirect on index as well and then problem is fixed. Signed-off-by: Vivek Goyal <vgoyal@redhat.com> Reviewed-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-05-11 15:49:32 +00:00
res = vfs_getxattr(dentry, name, buf, res);
if (res < 0)
goto fail;
}
*value = buf;
return res;
fail:
pr_warn_ratelimited("failed to get xattr %s: err=%zi)\n",
name, res);
kfree(buf);
return res;
}
ovl: Check redirect on index as well Right now we seem to check redirect only if upperdentry is found. But it is possible that there is no upperdentry but later we found an index. We need to check redirect on index as well and set it in ovl_inode->redirect. Otherwise link code can assume that dentry does not have redirect and place a new one which breaks things. In my testing overlay/033 test started failing in xfstests. Following are the details. For example do following. $ mkdir lower upper work merged - Make lower dir with 4 links. $ echo "foo" > lower/l0.txt $ ln lower/l0.txt lower/l1.txt $ ln lower/l0.txt lower/l2.txt $ ln lower/l0.txt lower/l3.txt - Mount with index on and metacopy on. $ mount -t overlay -o lowerdir=lower,upperdir=upper,workdir=work,\ index=on,metacopy=on none merged - Link lower $ ln merged/l0.txt merged/l4.txt (This will metadata copy up of l0.txt and put an absolute redirect /l0.txt) $ echo 2 > /proc/sys/vm/drop/caches $ ls merged/l1.txt (Now l1.txt will be looked up. There is no upper dentry but there is lower dentry and index will be found. We don't check for redirect on index, hence ovl_inode->redirect will be NULL.) - Link Upper $ ln merged/l4.txt merged/l5.txt (Lookup of l4.txt will use inode from l1.txt lookup which is still in cache. It has ovl_inode->redirect NULL, hence link will put a new redirect and replace /l0.txt with /l4.txt - Drop caches. echo 2 > /proc/sys/vm/drop_caches - List l1.txt and it returns -ESTALE $ ls merged/l0.txt (It returns stale because, we found a metacopy of l0.txt in upper and it has redirect l4.txt but there is no file named l4.txt in lower layer. So lower data copy is not found and -ESTALE is returned.) So problem here is that we did not process redirect on index. Check redirect on index as well and then problem is fixed. Signed-off-by: Vivek Goyal <vgoyal@redhat.com> Reviewed-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-05-11 15:49:32 +00:00
char *ovl_get_redirect_xattr(struct dentry *dentry, int padding)
{
int res;
char *s, *next, *buf = NULL;
res = ovl_getxattr(dentry, OVL_XATTR_REDIRECT, &buf, padding + 1);
if (res == -ENODATA)
return NULL;
ovl: Check redirect on index as well Right now we seem to check redirect only if upperdentry is found. But it is possible that there is no upperdentry but later we found an index. We need to check redirect on index as well and set it in ovl_inode->redirect. Otherwise link code can assume that dentry does not have redirect and place a new one which breaks things. In my testing overlay/033 test started failing in xfstests. Following are the details. For example do following. $ mkdir lower upper work merged - Make lower dir with 4 links. $ echo "foo" > lower/l0.txt $ ln lower/l0.txt lower/l1.txt $ ln lower/l0.txt lower/l2.txt $ ln lower/l0.txt lower/l3.txt - Mount with index on and metacopy on. $ mount -t overlay -o lowerdir=lower,upperdir=upper,workdir=work,\ index=on,metacopy=on none merged - Link lower $ ln merged/l0.txt merged/l4.txt (This will metadata copy up of l0.txt and put an absolute redirect /l0.txt) $ echo 2 > /proc/sys/vm/drop/caches $ ls merged/l1.txt (Now l1.txt will be looked up. There is no upper dentry but there is lower dentry and index will be found. We don't check for redirect on index, hence ovl_inode->redirect will be NULL.) - Link Upper $ ln merged/l4.txt merged/l5.txt (Lookup of l4.txt will use inode from l1.txt lookup which is still in cache. It has ovl_inode->redirect NULL, hence link will put a new redirect and replace /l0.txt with /l4.txt - Drop caches. echo 2 > /proc/sys/vm/drop_caches - List l1.txt and it returns -ESTALE $ ls merged/l0.txt (It returns stale because, we found a metacopy of l0.txt in upper and it has redirect l4.txt but there is no file named l4.txt in lower layer. So lower data copy is not found and -ESTALE is returned.) So problem here is that we did not process redirect on index. Check redirect on index as well and then problem is fixed. Signed-off-by: Vivek Goyal <vgoyal@redhat.com> Reviewed-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-05-11 15:49:32 +00:00
if (res < 0)
return ERR_PTR(res);
ovl: Check redirect on index as well Right now we seem to check redirect only if upperdentry is found. But it is possible that there is no upperdentry but later we found an index. We need to check redirect on index as well and set it in ovl_inode->redirect. Otherwise link code can assume that dentry does not have redirect and place a new one which breaks things. In my testing overlay/033 test started failing in xfstests. Following are the details. For example do following. $ mkdir lower upper work merged - Make lower dir with 4 links. $ echo "foo" > lower/l0.txt $ ln lower/l0.txt lower/l1.txt $ ln lower/l0.txt lower/l2.txt $ ln lower/l0.txt lower/l3.txt - Mount with index on and metacopy on. $ mount -t overlay -o lowerdir=lower,upperdir=upper,workdir=work,\ index=on,metacopy=on none merged - Link lower $ ln merged/l0.txt merged/l4.txt (This will metadata copy up of l0.txt and put an absolute redirect /l0.txt) $ echo 2 > /proc/sys/vm/drop/caches $ ls merged/l1.txt (Now l1.txt will be looked up. There is no upper dentry but there is lower dentry and index will be found. We don't check for redirect on index, hence ovl_inode->redirect will be NULL.) - Link Upper $ ln merged/l4.txt merged/l5.txt (Lookup of l4.txt will use inode from l1.txt lookup which is still in cache. It has ovl_inode->redirect NULL, hence link will put a new redirect and replace /l0.txt with /l4.txt - Drop caches. echo 2 > /proc/sys/vm/drop_caches - List l1.txt and it returns -ESTALE $ ls merged/l0.txt (It returns stale because, we found a metacopy of l0.txt in upper and it has redirect l4.txt but there is no file named l4.txt in lower layer. So lower data copy is not found and -ESTALE is returned.) So problem here is that we did not process redirect on index. Check redirect on index as well and then problem is fixed. Signed-off-by: Vivek Goyal <vgoyal@redhat.com> Reviewed-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-05-11 15:49:32 +00:00
if (res == 0)
goto invalid;
if (buf[0] == '/') {
for (s = buf; *s++ == '/'; s = next) {
next = strchrnul(s, '/');
if (s == next)
goto invalid;
}
} else {
if (strchr(buf, '/') != NULL)
goto invalid;
}
return buf;
invalid:
pr_warn_ratelimited("invalid redirect (%s)\n", buf);
ovl: Check redirect on index as well Right now we seem to check redirect only if upperdentry is found. But it is possible that there is no upperdentry but later we found an index. We need to check redirect on index as well and set it in ovl_inode->redirect. Otherwise link code can assume that dentry does not have redirect and place a new one which breaks things. In my testing overlay/033 test started failing in xfstests. Following are the details. For example do following. $ mkdir lower upper work merged - Make lower dir with 4 links. $ echo "foo" > lower/l0.txt $ ln lower/l0.txt lower/l1.txt $ ln lower/l0.txt lower/l2.txt $ ln lower/l0.txt lower/l3.txt - Mount with index on and metacopy on. $ mount -t overlay -o lowerdir=lower,upperdir=upper,workdir=work,\ index=on,metacopy=on none merged - Link lower $ ln merged/l0.txt merged/l4.txt (This will metadata copy up of l0.txt and put an absolute redirect /l0.txt) $ echo 2 > /proc/sys/vm/drop/caches $ ls merged/l1.txt (Now l1.txt will be looked up. There is no upper dentry but there is lower dentry and index will be found. We don't check for redirect on index, hence ovl_inode->redirect will be NULL.) - Link Upper $ ln merged/l4.txt merged/l5.txt (Lookup of l4.txt will use inode from l1.txt lookup which is still in cache. It has ovl_inode->redirect NULL, hence link will put a new redirect and replace /l0.txt with /l4.txt - Drop caches. echo 2 > /proc/sys/vm/drop_caches - List l1.txt and it returns -ESTALE $ ls merged/l0.txt (It returns stale because, we found a metacopy of l0.txt in upper and it has redirect l4.txt but there is no file named l4.txt in lower layer. So lower data copy is not found and -ESTALE is returned.) So problem here is that we did not process redirect on index. Check redirect on index as well and then problem is fixed. Signed-off-by: Vivek Goyal <vgoyal@redhat.com> Reviewed-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-05-11 15:49:32 +00:00
res = -EINVAL;
kfree(buf);
return ERR_PTR(res);
ovl: Check redirect on index as well Right now we seem to check redirect only if upperdentry is found. But it is possible that there is no upperdentry but later we found an index. We need to check redirect on index as well and set it in ovl_inode->redirect. Otherwise link code can assume that dentry does not have redirect and place a new one which breaks things. In my testing overlay/033 test started failing in xfstests. Following are the details. For example do following. $ mkdir lower upper work merged - Make lower dir with 4 links. $ echo "foo" > lower/l0.txt $ ln lower/l0.txt lower/l1.txt $ ln lower/l0.txt lower/l2.txt $ ln lower/l0.txt lower/l3.txt - Mount with index on and metacopy on. $ mount -t overlay -o lowerdir=lower,upperdir=upper,workdir=work,\ index=on,metacopy=on none merged - Link lower $ ln merged/l0.txt merged/l4.txt (This will metadata copy up of l0.txt and put an absolute redirect /l0.txt) $ echo 2 > /proc/sys/vm/drop/caches $ ls merged/l1.txt (Now l1.txt will be looked up. There is no upper dentry but there is lower dentry and index will be found. We don't check for redirect on index, hence ovl_inode->redirect will be NULL.) - Link Upper $ ln merged/l4.txt merged/l5.txt (Lookup of l4.txt will use inode from l1.txt lookup which is still in cache. It has ovl_inode->redirect NULL, hence link will put a new redirect and replace /l0.txt with /l4.txt - Drop caches. echo 2 > /proc/sys/vm/drop_caches - List l1.txt and it returns -ESTALE $ ls merged/l0.txt (It returns stale because, we found a metacopy of l0.txt in upper and it has redirect l4.txt but there is no file named l4.txt in lower layer. So lower data copy is not found and -ESTALE is returned.) So problem here is that we did not process redirect on index. Check redirect on index as well and then problem is fixed. Signed-off-by: Vivek Goyal <vgoyal@redhat.com> Reviewed-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-05-11 15:49:32 +00:00
}