linux/fs/debugfs/inode.c, branch v6.16

VFS: rename lookup_one_len family to lookup_noperm and remove permission check

2025-04-08T09:24:36Z

The lookup_one_len family of functions is (now) only used internally by a filesystem on itself either - in a context where permission checking is irrelevant such as by a virtual filesystem populating itself, or xfs accessing its ORPHANAGE or dquota accessing the quota file; or - in a context where a permission check (MAY_EXEC on the parent) has just been performed such as a network filesystem finding in "silly-rename" file in the same directory. This is also the context after the _parentat() functions where currently lookup_one_qstr_excl() is used. So the permission check is pointless. The name "one_len" is unhelpful in understanding the purpose of these functions and should be changed. Most of the callers pass the len as "strlen()" so using a qstr and QSTR() can simplify the code. This patch renames these functions (include lookup_positive_unlocked() which is part of the family despite the name) to have a name based on "lookup_noperm". They are changed to receive a 'struct qstr' instead of separate name and len. In a few cases the use of QSTR() results in a new call to strlen(). try_lookup_noperm() takes a pointer to a qstr instead of the whole qstr. This is consistent with d_hash_and_lookup() (which is nearly identical) and useful for lookup_noperm_unlocked(). The new lookup_noperm_common() doesn't take a qstr yet. That will be tidied up in a subsequent patch. Signed-off-by: NeilBrown Link: https://lore.kernel.org/r/20250319031545.2999807-5-neil@brown.name Signed-off-by: Christian Brauner

saner replacement for debugfs_rename()

2025-01-15T12:14:37Z

Existing primitive has several problems: 1) calling conventions are clumsy - it returns a dentry reference that is either identical to its second argument or is an ERR_PTR(-E...); in both cases no refcount changes happen. Inconvenient for users and bug-prone; it would be better to have it return 0 on success and -E... on failure. 2) it allows cross-directory moves; however, no such caller have ever materialized and considering the way debugfs is used, it's unlikely to happen in the future. What's more, any such caller would have fun issues to deal with wrt interplay with recursive removal. It also makes the calling conventions clumsier... 3) tautological rename fails; the callers have no race-free way to deal with that. 4) new name must have been formed by the caller; quite a few callers have it done by sprintf/kasprintf/etc., ending up with considerable boilerplate. Proposed replacement: int debugfs_change_name(dentry, fmt, ...). All callers convert to that easily, and it's simpler internally. IMO debugfs_rename() should go; if we ever get a real-world use case for cross-directory moves in debugfs, we can always look into the right way to handle that. Signed-off-by: Al Viro Link: https://lore.kernel.org/r/20250112080705.141166-21-viro@zeniv.linux.org.uk Signed-off-by: Greg Kroah-Hartman

debugfs: allow to store an additional opaque pointer at file creation

2025-01-15T12:14:36Z

Set by debugfs_create_file_aux(name, mode, parent, data, aux, fops). Plain debugfs_create_file() has it set to NULL. Accessed by debugfs_get_aux(file). Convenience macros for numeric opaque data - debugfs_create_file_aux_num and debugfs_get_aux_num, resp. Signed-off-by: Al Viro Reviewed-by: Christian Brauner Link: https://lore.kernel.org/r/20250112080705.141166-5-viro@zeniv.linux.org.uk Signed-off-by: Greg Kroah-Hartman

debugfs: don't mess with bits in ->d_fsdata

2025-01-15T12:14:35Z

The reason we need that crap is the dual use ->d_fsdata has there - it's both holding a debugfs_fsdata reference after the first debugfs_file_get() (actually, after the call of proxy ->open()) *and* it serves as a place to stash a reference to real file_operations from object creation to the first open. Oh, and it's triple use, actually - that stashed reference might be to debugfs_short_fops. Bugger that for a game of solidiers - just put the operations reference into debugfs-private augmentation of inode. And split debugfs_full_file_operations into full and short cases, so that debugfs_get_file() could tell one from another. Voila - ->d_fsdata holds NULL until the first (successful) debugfs_get_file() and a reference to struct debugfs_fsdata afterwards. Signed-off-by: Al Viro Reviewed-by: Christian Brauner Link: https://lore.kernel.org/r/20250112080705.141166-4-viro@zeniv.linux.org.uk Signed-off-by: Greg Kroah-Hartman

debugfs: move ->automount into debugfs_inode_info

2025-01-15T12:14:35Z

... and don't bother with debugfs_fsdata for those. Life's simpler that way... Signed-off-by: Al Viro Reviewed-by: Christian Brauner Link: https://lore.kernel.org/r/20250112080705.141166-2-viro@zeniv.linux.org.uk Signed-off-by: Greg Kroah-Hartman

debugfs: separate cache for debugfs inodes

2025-01-15T12:14:35Z

Embed them into container (struct debugfs_inode_info, with nothing else in it at the moment), set the cache up, etc. Just the infrastructure changes letting us augment debugfs inodes here; adding stuff will come at the next step. Signed-off-by: Al Viro Reviewed-by: Christian Brauner Link: https://lore.kernel.org/r/20250112080705.141166-1-viro@zeniv.linux.org.uk Signed-off-by: Greg Kroah-Hartman

debugfs: fix missing mutex_destroy() in short_fops case

2025-01-07T15:20:11Z

we need that in ->real_fops == NULL, ->short_fops != NULL case Fixes: 8dc6d81c6b2a "debugfs: add small file operations for most files" Signed-off-by: Al Viro Link: https://lore.kernel.org/r/20241229081223.3193228-1-viro@zeniv.linux.org.uk Signed-off-by: Greg Kroah-Hartman

fs: debugfs: differentiate short fops with proxy ops

2025-01-07T15:20:08Z

Geert reported that my previous short fops debugfs changes broke m68k, because it only has mandatory alignement of two, so we can't stash the "is it short" information into the pointer (as we already did with the "is it real" bit.) Instead, exploit the fact that debugfs_file_get() called on an already open file will already find that the fsdata is no longer the real fops but rather the allocated data that already distinguishes full/short ops, so only open() needs to be able to distinguish. We can achieve that by using two different open functions. Unfortunately this requires another set of full file ops, increasing the size by 536 bytes (x86-64), but that's still a reasonable trade-off given that only converting some of the wireless stack gained over 28k. This brings the total cost of this to around 1k, for wins of 28k (all x86-64). Reported-and-tested-by: Geert Uytterhoeven Link: https://lore.kernel.org/CAMuHMdWu_9-L2Te101w8hU7H_2yobJFPXSwwUmGHSJfaPWDKiQ@mail.gmail.com Fixes: 8dc6d81c6b2a ("debugfs: add small file operations for most files") Signed-off-by: Johannes Berg Tested-by: Geert Uytterhoeven Link: https://lore.kernel.org/r/20241129121536.30989-2-johannes@sipsolutions.net Signed-off-by: Greg Kroah-Hartman

debugfs: add small file operations for most files

2024-10-23T14:47:01Z

As struct file_operations is really big, but (most) debugfs files only use simple_open, read, write and perhaps seek, and don't need anything else, this wastes a lot of space for NULL pointers. Add a struct debugfs_short_fops and some bookkeeping code in debugfs so that users can use that with debugfs_create_file() using _Generic to figure out which function to use. Converting mac80211 to use it where possible saves quite a bit of space: 1010127 205064 1220 1216411 128f9b net/mac80211/mac80211.ko (before) 981199 205064 1220 1187483 121e9b net/mac80211/mac80211.ko (after) ------- -28928 = ~28KiB With a marginal space cost in debugfs: 8701 550 16 9267 2433 fs/debugfs/inode.o (before) 25233 325 32 25590 63f6 fs/debugfs/file.o (before) 8914 558 16 9488 2510 fs/debugfs/inode.o (after) 25380 325 32 25737 6489 fs/debugfs/file.o (after) --------------- +360 +8 (All on x86-64) A simple spatch suggests there are more than 300 instances, not even counting the ones hidden in macros like in mac80211, that could be trivially converted, for additional savings of about 240 bytes for each. Reviewed-by: Greg Kroah-Hartman Link: https://patch.msgid.link/20241022151838.26f9925fb959.Ia80b55e934bbfc45ce0df42a3233d34b35508046@changeid Signed-off-by: Johannes Berg

debugfs show actual source in /proc/mounts

2024-08-30T06:22:37Z

After its conversion to the new mount API, debugfs displays "none" in /proc/mounts instead of the actual source. Fix this by recognising its "source" mount option. Signed-off-by: Marc Aurèle La France Link: https://lore.kernel.org/r/e439fae2-01da-234b-75b9-2a7951671e27@tuyoix.net Fixes: a20971c18752 ("vfs: Convert debugfs to use the new mount API") Cc: stable@vger.kernel.org # 6.10.x: 49abee5991e1: debugfs: Convert to new uid/gid option parsing helpers Signed-off-by: Christian Brauner