kernel/linux.git/fs/super.c, branch v6.12.107

fs: unlock the superblock during iterate_supers_type

2026-08-23T12:22:51+00:00

commit 0b9d62a47149083d581d8b2abb04124b6175cb29 upstream. This function takes super_lock in shared mode, so it should release the same lock. Cc: stable@vger.kernel.org # v6.16-rc1 Fixes: af7551cf13cf7f ("super: remove pointless s_root checks") Signed-off-by: "Darrick J. Wong" Link: https://lore.kernel.org/20250611164044.GF6138@frogsfrogsfrogs Reviewed-by: Jan Kara Signed-off-by: Christian Brauner Signed-off-by: Greg Kroah-Hartman

super: fix emergency thaw deadlock on frozen block devices

2026-08-23T12:22:44+00:00

[ Upstream commit 749d7aa0377aae32af8c0a4ad43371e7bf830ab5 ] do_thaw_all_callback() calls bdev_thaw() while holding sb->s_umount exclusively. If the block device was frozen via bdev_freeze() dropping the last block layer freeze reference calls fs_bdev_thaw() which reacquires s_umount: do_thaw_all_callback(sb) super_lock_excl(sb) # holds sb->s_umount bdev_thaw(sb->s_bdev) mutex_lock(&bdev->bd_fsfreeze_mutex) # bd_fsfreeze_count drops 1 -> 0 bd_holder_ops->thaw == fs_bdev_thaw get_bdev_super(bdev) bdev_super_lock(bdev, true) super_lock(sb, true) down_write(&sb->s_umount) # same task: deadlock The emergency thaw worker deadlocks against itself holding both s_umount and bd_fsfreeze_mutex. That fscks any subsequent unmount, freeze, or thaw of that filesystem and block device. [ 81.878470] sysrq: Show Blocked State [ 81.880140] task:kworker/0:1 state:D stack:0 pid:11 tgid:11 ppid:2 task_flags:0x4208060 flags:0x00080000 [ 81.884876] Workqueue: events do_thaw_all [ 81.886656] Call Trace: [ 81.887759] [ 81.888763] __schedule+0x579/0x1420 [ 81.890372] schedule+0x3a/0x100 [ 81.891794] schedule_preempt_disabled+0x15/0x30 [ 81.893848] rwsem_down_write_slowpath+0x1ea/0x900 [ 81.895191] ? __pfx_do_thaw_all_callback+0x10/0x10 [ 81.896528] down_write+0xbd/0xc0 [ 81.897505] super_lock+0x91/0x180 [ 81.898457] ? __mutex_lock+0xa99/0x1140 [ 81.900748] ? __mutex_unlock_slowpath+0x1f/0x400 [ 81.902069] bdev_super_lock+0x5b/0x150 [ 81.903132] get_bdev_super+0x10/0x60 [ 81.904042] fs_bdev_thaw+0x23/0xf0 [ 81.904755] bdev_thaw+0x82/0x100 [ 81.905484] do_thaw_all_callback+0x2c/0x50 [ 81.906298] __iterate_supers+0x5d/0x130 [ 81.907067] do_thaw_all+0x20/0x40 [ 81.907739] process_one_work+0x206/0x5e0 [ 81.908545] worker_thread+0x1e2/0x3c0 [ 81.909339] ? __pfx_worker_thread+0x10/0x10 [ 81.910171] kthread+0xf4/0x130 [ 81.910799] ? __pfx_kthread+0x10/0x10 [ 81.911528] ret_from_fork+0x2e2/0x3b0 [ 81.912259] ? __pfx_kthread+0x10/0x10 [ 81.913010] ret_from_fork_asm+0x1a/0x30 [ 81.913806] bdev_super_lock() even documents the violated requirement with lockdep_assert_not_held(&sb->s_umount). Acquiring bd_fsfreeze_mutex under s_umount also inverts the bd_fsfreeze_mutex vs. s_umount ordering established by bdev_{freeze,thaw}() and can thus ABBA against a concurrent block-layer freeze even when the recursive path isn't hit. Fix this by not holding s_umount around the bdev_thaw() loop at all. Pin the superblock with an active reference instead as filesystems_freeze_callback() does. The active reference keeps the superblock from being shut down and so ->s_bdev stays valid without holding s_umount. The block-layer-held freeze is dropped by fs_bdev_thaw() with FREEZE_MAY_NEST | FREEZE_HOLDER_USERSPACE exactly as a regular unfreeze would and thaw_super_locked() handles filesystem-level freezes as before. The emergency thaw path has deadlocked like this in one form or another for a long long time but the current exclusively-held shape dates back to commit [1] where thaw_bdev() already ended in thaw_super() with s_umount held by do_thaw_all_callback(). Fixes: 08fdc8a0138a ("buffer.c: call thaw_super during emergency thaw") [1] Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20260723-work-super-emergency_thaw-v1-1-7c315c600245@kernel.org Signed-off-by: Christian Brauner (Amutable) Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

fs/super: fix emergency thaw double-unlock of s_umount

2026-08-23T12:22:44+00:00

[ Upstream commit 503d67fbaec6fdeaba391cb497675071db9d16ea ] do_thaw_all() iterates over all superblocks via __iterate_supers() with SUPER_ITER_EXCL, which acquires s_umount exclusively before calling the callback and releases it afterwards. However, the callback do_thaw_all_callback() calls thaw_super_locked() which unconditionally releases s_umount on every code path. This results in a second unlock attempt in __iterate_supers() that corrupts the rwsem state, triggering a DEBUG_RWSEMS warning: [ 182.601148] sysrq: Emergency Thaw of all frozen filesystems [ 182.601865] ------------[ cut here ]------------ [ 182.602375] DEBUG_RWSEMS_WARN_ON((rwsem_owner(sem) != current) && !rwsem_test_oflags(sem, RWSEM_NONSPINNABLE)): count = 0x0, magic = 0xffff99b1011e5870, owner = 0x0, curr 0xffff99b101b06c80, list not empty [ 182.603817] WARNING: kernel/locking/rwsem.c:1412 at up_write+0xa3/0x170, CPU#2: kworker/2:1/53 [ 182.604578] Modules linked in: [ 182.604864] CPU: 2 UID: 0 PID: 53 Comm: kworker/2:1 Not tainted 7.2.0-rc4-00001-gbd3bd93ea98a-dirty #4 PREEMPT(lazy) [ 182.605711] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1kylin1 04/01/2014 [ 182.606417] Workqueue: events do_thaw_all [ 182.606750] RIP: 0010:up_write+0xaf/0x170 [ 182.607076] Code: 19 3a 92 48 0f 44 c2 48 8b 55 08 48 8b 55 00 4c 8b 45 08 48 8b 55 00 48 8d 3d ad 91 e0 01 48 8b 4d 20 50 48 c7 c6 f0 8c 26 92 <67> 48 0f b9 3a e8 d7 93 4e 00 58 eb 81 48 83 7f 18 00 48 c7 c2 8d [ 182.608563] RSP: 0018:ffffb670001d7e08 EFLAGS: 00010246 [ 182.609007] RAX: ffffffff92349e8d RBX: 0000000000000000 RCX: ffff99b1011e5870 [ 182.609595] RDX: 0000000000000000 RSI: ffffffff92268cf0 RDI: ffffffff92914d10 [ 182.610283] RBP: ffff99b1011e5870 R08: 0000000000000000 R09: ffff99b101b06c80 [ 182.610847] R10: ffff99b10139a808 R11: fefefefefefefeff R12: 0000000000000000 [ 182.611414] R13: ffffffff90cf74d0 R14: 0000000000000000 R15: ffff99b1011e5800 [ 182.612009] FS: 0000000000000000(0000) GS:ffff99b1eaaee000(0000) knlGS:0000000000000000 [ 182.612670] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 182.613146] CR2: 00000000005c631c CR3: 00000000013ee000 CR4: 00000000000006f0 [ 182.613722] Call Trace: [ 182.613946] [ 182.614130] __iterate_supers+0x128/0x150 [ 182.614463] do_thaw_all+0x1b/0x30 [ 182.614759] process_scheduled_works+0xbb/0x3f0 [ 182.615150] ? __pfx_worker_thread+0x10/0x10 [ 182.615499] worker_thread+0x129/0x270 [ 182.615816] ? __pfx_worker_thread+0x10/0x10 [ 182.616201] kthread+0xe2/0x120 [ 182.616469] ? __pfx_kthread+0x10/0x10 [ 182.616792] ret_from_fork+0x15b/0x240 [ 182.617115] ? __pfx_kthread+0x10/0x10 [ 182.617426] ret_from_fork_asm+0x1a/0x30 [ 182.617761] [ 182.617968] ---[ end trace 0000000000000000 ]--- [ 182.618412] Emergency Thaw complete Fix this by switching to SUPER_ITER_UNLOCKED and acquiring s_umount in the callback via super_lock_excl() before calling thaw_super_locked(). This matches the locking pattern expected by thaw_super_locked() and eliminates the double unlock. While at it, remove the dead 'return;' at the end of do_thaw_all_callback(). Fixes: 2992476528ae ("super: use a common iterator (Part 1)") Cc: stable@vger.kernel.org Signed-off-by: Chen Changcheng Link: https://patch.msgid.link/20260721064140.152305-1-chenchangcheng@kylinos.cn Signed-off-by: Christian Brauner (Amutable) Stable-dep-of: 749d7aa0377a ("super: fix emergency thaw deadlock on frozen block devices") Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

super: use common iterator (Part 2)

2026-08-23T12:22:44+00:00

[ Upstream commit b47e42d10e8c20525febccbd6e0dc8528861aea4 ] Use a common iterator for all callbacks. We could go for something even more elaborate (advance step-by-step similar to iov_iter) but I really don't think this is warranted. Link: https://lore.kernel.org/r/20250329-work-freeze-v2-5-a47af37ecc3d@kernel.org Reviewed-by: Jan Kara Signed-off-by: Christian Brauner Stable-dep-of: 749d7aa0377a ("super: fix emergency thaw deadlock on frozen block devices") Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

super: use a common iterator (Part 1)

2026-08-23T12:22:44+00:00

[ Upstream commit 2992476528aeecbaee17ba0a6396a817481205a3 ] Use a common iterator for all callbacks. Link: https://lore.kernel.org/r/20250329-work-freeze-v2-4-a47af37ecc3d@kernel.org Reviewed-by: Jan Kara Signed-off-by: Christian Brauner Stable-dep-of: 749d7aa0377a ("super: fix emergency thaw deadlock on frozen block devices") Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

super: skip dying superblocks early

2026-08-23T12:22:44+00:00

[ Upstream commit 6920e3388ba4c66b0468d43bb7a373f5fff15d35 ] Make all iterators uniform by performing an early check whether the superblock is dying. Link: https://lore.kernel.org/r/20250329-work-freeze-v2-3-a47af37ecc3d@kernel.org Reviewed-by: Jan Kara Signed-off-by: Christian Brauner Stable-dep-of: 749d7aa0377a ("super: fix emergency thaw deadlock on frozen block devices") Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

super: remove pointless s_root checks

2026-08-23T12:22:44+00:00

[ Upstream commit af7551cf13cf7fb1d4f939db4f1f24c00550ed57 ] The locking guarantees that the superblock is alive and sb->s_root is still set. Remove the pointless check. Link: https://lore.kernel.org/r/20250329-work-freeze-v2-1-a47af37ecc3d@kernel.org Reviewed-by: Jan Kara Signed-off-by: Christian Brauner Stable-dep-of: 749d7aa0377a ("super: fix emergency thaw deadlock on frozen block devices") Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

fs/super.c: introduce get_tree_bdev_flags()

2024-10-21T12:30:26+00:00

As Allison reported [1], currently get_tree_bdev() will store "Can't lookup blockdev" error message. Although it makes sense for pure bdev-based fses, this message may mislead users who try to use EROFS file-backed mounts since get_tree_nodev() is used as a fallback then. Add get_tree_bdev_flags() to specify extensible flags [2] and GET_TREE_BDEV_QUIET_LOOKUP to silence "Can't lookup blockdev" message since it's misleading to EROFS file-backed mounts now. [1] https://lore.kernel.org/r/CAOYeF9VQ8jKVmpy5Zy9DNhO6xmWSKMB-DO8yvBB0XvBE7=3Ugg@mail.gmail.com [2] https://lore.kernel.org/r/ZwUkJEtwIpUA4qMz@infradead.org Suggested-by: Christoph Hellwig Signed-off-by: Gao Xiang Link: https://lore.kernel.org/r/20241009033151.2334888-1-hsiangkao@linux.alibaba.com Reviewed-by: Christoph Hellwig Reviewed-by: Jan Kara Signed-off-by: Christian Brauner

Merge tag 'vfs-6.12.misc' of gitolite.kernel.org:pub/scm/linux/kernel/git/vfs/vfs

2024-09-16T06:35:09+00:00

Pull misc vfs updates from Christian Brauner: "This contains the usual pile of misc updates: Features: - Add F_CREATED_QUERY fcntl() that allows userspace to query whether a file was actually created. Often userspace wants to know whether an O_CREATE request did actually create a file without using O_EXCL. The current logic is that to first attempts to open the file without O_CREAT | O_EXCL and if ENOENT is returned userspace tries again with both flags. If that succeeds all is well. If it now reports EEXIST it retries. That works fairly well but some corner cases make this more involved. If this operates on a dangling symlink the first openat() without O_CREAT | O_EXCL will return ENOENT but the second openat() with O_CREAT | O_EXCL will fail with EEXIST. The reason is that openat() without O_CREAT | O_EXCL follows the symlink while O_CREAT | O_EXCL doesn't for security reasons. So it's not something we can really change unless we add an explicit opt-in via O_FOLLOW which seems really ugly. All available workarounds are really nasty (fanotify, bpf lsm etc) so add a simple fcntl(). - Try an opportunistic lookup for O_CREAT. Today, when opening a file we'll typically do a fast lookup, but if O_CREAT is set, the kernel always takes the exclusive inode lock. This was likely done with the expectation that O_CREAT means that we always expect to do the create, but that's often not the case. Many programs set O_CREAT even in scenarios where the file already exists (see related F_CREATED_QUERY patch motivation above). The series contained in the pr rearranges the pathwalk-for-open code to also attempt a fast_lookup in certain O_CREAT cases. If a positive dentry is found, the inode_lock can be avoided altogether and it can stay in rcuwalk mode for the last step_into. - Expose the 64 bit mount id via name_to_handle_at() Now that we provide a unique 64-bit mount ID interface in statx(2), we can now provide a race-free way for name_to_handle_at(2) to provide a file handle and corresponding mount without needing to worry about racing with /proc/mountinfo parsing or having to open a file just to do statx(2). While this is not necessary if you are using AT_EMPTY_PATH and don't care about an extra statx(2) call, users that pass full paths into name_to_handle_at(2) need to know which mount the file handle comes from (to make sure they don't try to open_by_handle_at a file handle from a different filesystem) and switching to AT_EMPTY_PATH would require allocating a file for every name_to_handle_at(2) call - Add a per dentry expire timeout to autofs There are two fairly well known automounter map formats, the autofs format and the amd format (more or less System V and Berkley). Some time ago Linux autofs added an amd map format parser that implemented a fair amount of the amd functionality. This was done within the autofs infrastructure and some functionality wasn't implemented because it either didn't make sense or required extra kernel changes. The idea was to restrict changes to be within the existing autofs functionality as much as possible and leave changes with a wider scope to be considered later. One of these changes is implementing the amd options: 1) "unmount", expire this mount according to a timeout (same as the current autofs default). 2) "nounmount", don't expire this mount (same as setting the autofs timeout to 0 except only for this specific mount) . 3) "utimeout=", expire this mount using the specified timeout (again same as setting the autofs timeout but only for this mount) To implement these options per-dentry expire timeouts need to be implemented for autofs indirect mounts. This is because all map keys (mounts) for autofs indirect mounts use an expire timeout stored in the autofs mount super block info. structure and all indirect mounts use the same expire timeout. Fixes: - Fix missing fput for FSCONFIG_SET_FD in autofs - Use param->file for FSCONFIG_SET_FD in coda - Delete the 'fs/netfs' proc subtreee when netfs module exits - Make sure that struct uid_gid_map fits into a single cacheline - Don't flush in-flight wb switches for superblocks without cgroup writeback - Correcting the idmapping mount example in the idmapping documentation - Fix a race between evice_inodes() and find_inode() and iput() - Refine the show_inode_state() macro definition in writeback code - Prevent dump_mapping() from accessing invalid dentry.d_name.name - Show actual source for debugfs in /proc/mounts - Annotate data-race of busy_poll_usecs in eventpoll - Don't WARN for racy path_noexec check in exec code - Handle OOM on mnt_warn_timestamp_expiry() - Fix some spelling in the iomap design documentation - Fix typo in procfs comment - Fix typo in fs/namespace.c comment Cleanups: - Add the VFS git tree to the MAINTAINERS file - Move FMODE_UNSIGNED_OFFSET to fop_flags freeing up another f_mode bit in struct file bringing us to 5 free f_mode bits - Remove the __I_DIO_WAKEUP bit from i_state flags as we can simplify the wait mechanism - Remove the unused path_put_init() helper - Replace a __u32 with u32 for s_fsnotify_mask as __u32 is uapi specific - Replace the unsigned long i_state member with a u32 i_state member in struct inode freeing up 4 bytes in struct inode. Instead of using the bit based wait apis we're now using the var event apis and using the individual bytes of the i_state member to wait on state changes - Explain how per-syscall AT_* flags should be allocated - Use in_group_or_capable() helper to simplify the posix acl mode update code - Switch to LIST_HEAD() in fsync_buffers_list() to simplify the code - Removed comment about d_rcu_to_refcount() as that function doesn't exist anymore - Add kernel documentation for lookup_fast() - Don't re-zero evenpoll fields - Remove outdated comment after close_fd() - Fix imprecise wording in comment about the pipe filesystem - Drop GFP_NOFAIL mode from alloc_page_buffers - Missing blank line warnings and struct declaration improved in file_table - Annotate struct poll_list with __counted_by() - Remove the unused read parameter in percpu-rwsem - Remove linux/prefetch.h include from direct-io code - Use kmemdup_array instead of kmemdup for multiple allocation in mnt_idmapping code - Remove unused mnt_cursor_del() declaration Performance tweaks: - Dodge smp_mb in break_lease and break_deleg in the common case - Only read fops once in fops_{get,put}() - Use RCU in ilookup() - Elide smp_mb in iversion handling in the common case - Drop one lock trip in evict()" * tag 'vfs-6.12.misc' of gitolite.kernel.org:pub/scm/linux/kernel/git/vfs/vfs: (58 commits) uidgid: make sure we fit into one cacheline proc: Fix typo in the comment fs/pipe: Correct imprecise wording in comment fhandle: expose u64 mount id to name_to_handle_at(2) uapi: explain how per-syscall AT_* flags should be allocated fs: drop GFP_NOFAIL mode from alloc_page_buffers writeback: Refine the show_inode_state() macro definition fs/inode: Prevent dump_mapping() accessing invalid dentry.d_name.name mnt_idmapping: Use kmemdup_array instead of kmemdup for multiple allocation netfs: Delete subtree of 'fs/netfs' when netfs module exits fs: use LIST_HEAD() to simplify code inode: make i_state a u32 inode: port __I_LRU_ISOLATING to var event vfs: fix race between evice_inodes() and find_inode()&iput() inode: port __I_NEW to var event inode: port __I_SYNC to var event fs: reorder i_state bits fs: add i_state helpers MAINTAINERS: add the VFS git tree fs: s/__u32/u32/ for s_fsnotify_mask ...

fs/super.c: improve get_tree() error message

2024-08-22T06:07:23+00:00

seeing an odd bug where we fail to correctly return an error from .get_tree(): https://syzkaller.appspot.com/bug?extid=c0360e8367d6d8d04a66 we need to be able to distinguish between accidently returning a positive error (as implied by the log) and no error. Cc: David Howells Signed-off-by: Kent Overstreet