kernel.git/fs/autofs/root.c, branch linux-6.15.y

Change inode_operations.mkdir to return struct dentry *

2025-02-27T19:00:17Z

Some filesystems, such as NFS, cifs, ceph, and fuse, do not have complete control of sequencing on the actual filesystem (e.g. on a different server) and may find that the inode created for a mkdir request already exists in the icache and dcache by the time the mkdir request returns. For example, if the filesystem is mounted twice the directory could be visible on the other mount before it is on the original mount, and a pair of name_to_handle_at(), open_by_handle_at() calls could instantiate the directory inode with an IS_ROOT() dentry before the first mkdir returns. This means that the dentry passed to ->mkdir() may not be the one that is associated with the inode after the ->mkdir() completes. Some callers need to interact with the inode after the ->mkdir completes and they currently need to perform a lookup in the (rare) case that the dentry is no longer hashed. This lookup-after-mkdir requires that the directory remains locked to avoid races. Planned future patches to lock the dentry rather than the directory will mean that this lookup cannot be performed atomically with the mkdir. To remove this barrier, this patch changes ->mkdir to return the resulting dentry if it is different from the one passed in. Possible returns are: NULL - the directory was created and no other dentry was used ERR_PTR() - an error occurred non-NULL - this other dentry was spliced in This patch only changes file-systems to return "ERR_PTR(err)" instead of "err" or equivalent transformations. Subsequent patches will make further changes to some file-systems to return a correct dentry. Not all filesystems reliably result in a positive hashed dentry: - NFS, cifs, hostfs will sometimes need to perform a lookup of the name to get inode information. Races could result in this returning something different. Note that this lookup is non-atomic which is what we are trying to avoid. Placing the lookup in filesystem code means it only happens when the filesystem has no other option. - kernfs and tracefs leave the dentry negative and the ->revalidate operation ensures that lookup will be called to correctly populate the dentry. This could be fixed but I don't think it is important to any of the users of vfs_mkdir() which look at the dentry. The recommendation to use d_drop();d_splice_alias() is ugly but fits with current practice. A planned future patch will change this. Reviewed-by: Jeff Layton Reviewed-by: Jan Kara Signed-off-by: NeilBrown Link: https://lore.kernel.org/r/20250227013949.536172-2-neilb@suse.de Signed-off-by: Christian Brauner

autofs: convert to new timestamp accessors

2023-10-18T11:26:18Z

Convert to using the new inode timestamp accessor functions. Signed-off-by: Jeff Layton Link: https://lore.kernel.org/r/20231004185347.80880-17-jlayton@kernel.org Signed-off-by: Christian Brauner

autofs: convert to ctime accessor functions

2023-07-13T08:28:04Z

In later patches, we're going to change how the inode's ctime field is used. Switch to using accessor functions instead of raw accesses of inode->i_ctime. Reviewed-by: Ian Kent Reviewed-by: Jan Kara Signed-off-by: Jeff Layton Message-Id: <20230705190309.579783-24-jlayton@kernel.org> Signed-off-by: Christian Brauner

autofs: set ctime as well when mtime changes on a dir

2023-06-15T07:22:24Z

When adding entries to a directory, POSIX generally requires that the ctime also be updated alongside the mtime. Signed-off-by: Jeff Layton Acked-by: Ian Kent Message-Id: <20230612104524.17058-4-jlayton@kernel.org> Signed-off-by: Christian Brauner

fs: port ->permission() to pass mnt_idmap

2023-01-19T08:24:28Z

Convert to struct mnt_idmap. Last cycle we merged the necessary infrastructure in 256c8aed2b42 ("fs: introduce dedicated idmap type for mounts"). This is just the conversion to struct mnt_idmap. Currently we still pass around the plain namespace that was attached to a mount. This is in general pretty convenient but it makes it easy to conflate namespaces that are relevant on the filesystem with namespaces that are relevent on the mount level. Especially for non-vfs developers without detailed knowledge in this area this can be a potential source for bugs. Once the conversion to struct mnt_idmap is done all helpers down to the really low-level helpers will take a struct mnt_idmap argument instead of two namespace arguments. This way it becomes impossible to conflate the two eliminating the possibility of any bugs. All of the vfs and all filesystems only operate on struct mnt_idmap. Acked-by: Dave Chinner Reviewed-by: Christoph Hellwig Signed-off-by: Christian Brauner (Microsoft)

fs: port ->mkdir() to pass mnt_idmap

2023-01-19T08:24:26Z

fs: port ->symlink() to pass mnt_idmap

2023-01-19T08:24:25Z

autofs: add comment about autofs_mountpoint_changed()

2022-07-18T00:31:42Z

The function autofs_mountpoint_changed() is unusual, add a comment about two cases for which it is needed. Link: https://lkml.kernel.org/r/165724459804.30914.10974834416046555127.stgit@donald.themaw.net Signed-off-by: Ian Kent Cc: Al Viro Cc: David Howells Cc: Miklos Szeredi Signed-off-by: Andrew Morton

autofs: use dentry info count instead of simple_empty()

2022-07-18T00:31:42Z

The dentry info. field count is used to check if a dentry is in use during expire. But, to be used for this the count field must account for the presence of child dentries in a directory dentry. Therefore it can also be used to check for an empty directory dentry which can be done without having to to take an additional lock or account for the presence of a readdir cursor dentry as is done by simple_empty(). Link: https://lkml.kernel.org/r/165724459238.30914.1504611159945950108.stgit@donald.themaw.net Signed-off-by: Ian Kent Cc: Al Viro Cc: David Howells Cc: Miklos Szeredi Signed-off-by: Andrew Morton

autofs: make dentry info count consistent

2022-07-18T00:31:42Z

If an autofs dentry is a mount root directory there's no ->mkdir() call to set its count to one. To make the dentry info count consistent for all autofs dentries set count to one when the dentry info struct is allocated. Link: https://lkml.kernel.org/r/165724458671.30914.2902424437132835325.stgit@donald.themaw.net Signed-off-by: Ian Kent Cc: Al Viro Cc: David Howells Cc: Miklos Szeredi Signed-off-by: Andrew Morton