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libfs: Fix simple_offset_rename_exchange()

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User space expects the replacement (old) directory entry to have
the same directory offset after the rename.

Suggested-by: Christian Brauner <brauner@kernel.org>
Fixes: a2e459555c5f ("shmem: stable directory offsets")
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Link: https://lore.kernel.org/r/20240415152057.4605-2-cel@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
Chuck Lever 2024-04-15 11:20:54 -04:00 committed by Christian Brauner
parent 4cece76496
commit 23cdd0eed3
No known key found for this signature in database
GPG Key ID: 91C61BC06578DCA2
1 changed files with 19 additions and 6 deletions
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25
fs/libfs.c
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@ -295,6 +295,18 @@ int simple_offset_add(struct offset_ctx *octx, struct dentry *dentry)
return 0;
}
static int simple_offset_replace(struct offset_ctx *octx, struct dentry *dentry,
long offset)
{
int ret;
ret = mtree_store(&octx->mt, offset, dentry, GFP_KERNEL);
if (ret)
return ret;
offset_set(dentry, offset);
return 0;
}
/**
* simple_offset_remove - Remove an entry to a directory's offset map
* @octx: directory offset ctx to be updated
@ -352,6 +364,9 @@ int simple_offset_empty(struct dentry *dentry)
* @new_dir: destination parent
* @new_dentry: destination dentry
*
* This API preserves the directory offset values. Caller provides
* appropriate serialization.
*
* Returns zero on success. Otherwise a negative errno is returned and the
* rename is rolled back.
*/
@ -369,11 +384,11 @@ int simple_offset_rename_exchange(struct inode *old_dir,
simple_offset_remove(old_ctx, old_dentry);
simple_offset_remove(new_ctx, new_dentry);
ret = simple_offset_add(new_ctx, old_dentry);
ret = simple_offset_replace(new_ctx, old_dentry, new_index);
if (ret)
goto out_restore;
ret = simple_offset_add(old_ctx, new_dentry);
ret = simple_offset_replace(old_ctx, new_dentry, old_index);
if (ret) {
simple_offset_remove(new_ctx, old_dentry);
goto out_restore;
@ -388,10 +403,8 @@ int simple_offset_rename_exchange(struct inode *old_dir,
return 0;
out_restore:
offset_set(old_dentry, old_index);
mtree_store(&old_ctx->mt, old_index, old_dentry, GFP_KERNEL);
offset_set(new_dentry, new_index);
mtree_store(&new_ctx->mt, new_index, new_dentry, GFP_KERNEL);
(void)simple_offset_replace(old_ctx, old_dentry, old_index);
(void)simple_offset_replace(new_ctx, new_dentry, new_index);
return ret;
}