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VFS/nfsd/cachefiles/ovl: introduce start_removing() and end_removing()

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start_removing() is similar to start_creating() but will only return a
positive dentry with the expectation that it will be removed.  This is
used by nfsd, cachefiles, and overlayfs.  They are changed to also use
end_removing() to terminate the action begun by start_removing().  This
is a simple alias for end_dirop().

Apart from changes to the error paths, as we no longer need to unlock on
a lookup error, an effect on callers is that they don't need to test if
the found dentry is positive or negative - they can be sure it is
positive.

Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: NeilBrown <neil@brown.name>
Link: https://patch.msgid.link/20251113002050.676694-6-neilb@ownmail.net
Tested-by: syzbot@syzkaller.appspotmail.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
NeilBrown
2025-11-13 11:18:28 +11:00
committed by Christian Brauner
parent 7ab96df840
commit bd6ede8a06
7 changed files with 89 additions and 55 deletions
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32
fs/cachefiles/namei.c
View File

@@ -260,6 +260,7 @@ static int cachefiles_unlink(struct cachefiles_cache *cache,
* - File backed objects are unlinked
* - Directory backed objects are stuffed into the graveyard for userspace to
* delete
* On entry dir must be locked. It will be unlocked on exit.
*/
int cachefiles_bury_object(struct cachefiles_cache *cache,
struct cachefiles_object *object,
@@ -274,28 +275,30 @@ int cachefiles_bury_object(struct cachefiles_cache *cache,
_enter(",'%pd','%pd'", dir, rep);
/* end_removing() will dput() @rep but we need to keep
* a ref, so take one now. This also stops the dentry
* being negated when unlinked which we need.
*/
dget(rep);
if (rep->d_parent != dir) {
inode_unlock(d_inode(dir));
end_removing(rep);
_leave(" = -ESTALE");
return -ESTALE;
}
/* non-directories can just be unlinked */
if (!d_is_dir(rep)) {
dget(rep); /* Stop the dentry being negated if it's only pinned
* by a file struct.
*/
ret = cachefiles_unlink(cache, object, dir, rep, why);
dput(rep);
end_removing(rep);
inode_unlock(d_inode(dir));
_leave(" = %d", ret);
return ret;
}
/* directories have to be moved to the graveyard */
_debug("move stale object to graveyard");
inode_unlock(d_inode(dir));
end_removing(rep);
try_again:
/* first step is to make up a grave dentry in the graveyard */
@@ -749,26 +752,20 @@ static struct dentry *cachefiles_lookup_for_cull(struct cachefiles_cache *cache,
struct dentry *victim;
int ret = -ENOENT;
inode_lock_nested(d_inode(dir), I_MUTEX_PARENT);
victim = start_removing(&nop_mnt_idmap, dir, &QSTR(filename));
victim = lookup_one(&nop_mnt_idmap, &QSTR(filename), dir);
if (IS_ERR(victim))
goto lookup_error;
if (d_is_negative(victim))
goto lookup_put;
if (d_inode(victim)->i_flags & S_KERNEL_FILE)
goto lookup_busy;
return victim;
lookup_busy:
ret = -EBUSY;
lookup_put:
inode_unlock(d_inode(dir));
dput(victim);
end_removing(victim);
return ERR_PTR(ret);
lookup_error:
inode_unlock(d_inode(dir));
ret = PTR_ERR(victim);
if (ret == -ENOENT)
return ERR_PTR(-ESTALE); /* Probably got retired by the netfs */
@@ -816,18 +813,17 @@ int cachefiles_cull(struct cachefiles_cache *cache, struct dentry *dir,
ret = cachefiles_bury_object(cache, NULL, dir, victim,
FSCACHE_OBJECT_WAS_CULLED);
dput(victim);
if (ret < 0)
goto error;
fscache_count_culled();
dput(victim);
_leave(" = 0");
return 0;
error_unlock:
inode_unlock(d_inode(dir));
end_removing(victim);
error:
dput(victim);
if (ret == -ENOENT)
return -ESTALE; /* Probably got retired by the netfs */