From c54b386969a58151765a9ffaaa0438e7b580283f Mon Sep 17 00:00:00 2001 From: NeilBrown Date: Thu, 27 Feb 2025 12:32:58 +1100 Subject: VFS: Change vfs_mkdir() to return the dentry. vfs_mkdir() does not guarantee to leave the child dentry hashed or make it positive on success, and in many such cases the filesystem had to use a different dentry which it can now return. This patch changes vfs_mkdir() to return the dentry provided by the filesystems which is hashed and positive when provided. This reduces the number of cases where the resulting dentry is not positive to a handful which don't deserve extra efforts. The only callers of vfs_mkdir() which are interested in the resulting inode are in-kernel filesystem clients: cachefiles, nfsd, smb/server. The only filesystems that don't reliably provide the inode are: - kernfs, tracefs which these clients are unlikely to be interested in - cifs in some configurations would need to do a lookup to find the created inode, but doesn't. cifs cannot be exported via NFS, is unlikely to be used by cachefiles, and smb/server only has a soft requirement for the inode, so this is unlikely to be a problem in practice. - hostfs, nfs, cifs may need to do a lookup (rarely for NFS) and it is possible for a race to make that lookup fail. Actual failure is unlikely and providing callers handle negative dentries graceful they will fail-safe. So this patch removes the lookup code in nfsd and smb/server and adjusts them to fail safe if a negative dentry is provided: - cache-files already fails safe by restarting the task from the top - it still does with this change, though it no longer calls cachefiles_put_directory() as that will crash if the dentry is negative. - nfsd reports "Server-fault" which it what it used to do if the lookup failed. This will never happen on any file-systems that it can actually export, so this is of no consequence. I removed the fh_update() call as that is not needed and out-of-place. A subsequent nfsd_create_setattr() call will call fh_update() when needed. - smb/server only wants the inode to call ksmbd_smb_inherit_owner() which updates ->i_uid (without calling notify_change() or similar) which can be safely skipping on cifs (I hope). If a different dentry is returned, the first one is put. If necessary the fact that it is new can be determined by comparing pointers. A new dentry will certainly have a new pointer (as the old is put after the new is obtained). Similarly if an error is returned (via ERR_PTR()) the original dentry is put. Reviewed-by: Jeff Layton Signed-off-by: NeilBrown Link: https://lore.kernel.org/r/20250227013949.536172-7-neilb@suse.de Signed-off-by: Christian Brauner --- fs/ecryptfs/inode.c | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-) (limited to 'fs/ecryptfs/inode.c') diff --git a/fs/ecryptfs/inode.c b/fs/ecryptfs/inode.c index 6315dd194228..51a5c54eb740 100644 --- a/fs/ecryptfs/inode.c +++ b/fs/ecryptfs/inode.c @@ -511,10 +511,16 @@ static struct dentry *ecryptfs_mkdir(struct mnt_idmap *idmap, struct inode *dir, struct inode *lower_dir; rc = lock_parent(dentry, &lower_dentry, &lower_dir); - if (!rc) - rc = vfs_mkdir(&nop_mnt_idmap, lower_dir, - lower_dentry, mode); - if (rc || d_really_is_negative(lower_dentry)) + if (rc) + goto out; + + lower_dentry = vfs_mkdir(&nop_mnt_idmap, lower_dir, + lower_dentry, mode); + rc = PTR_ERR(lower_dentry); + if (IS_ERR(lower_dentry)) + goto out; + rc = 0; + if (d_unhashed(lower_dentry)) goto out; rc = ecryptfs_interpose(lower_dentry, dentry, dir->i_sb); if (rc) -- cgit v1.2.3