[trivial conflict in Documentation/filesystems/porting.rst] The following changes since commit 19272b37aa4f83ca52bdf9c16d5d81bdd1354494: Linux 6.16-rc1 (2025-06-08 13:44:43 -0700) are available in the Git repository at: git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs.git tags/pull-dcache for you to fetch changes up to a509e7cf622bc7ce3f45b1c7047fc2a5e9bea869: configfs: use DCACHE_DONTCACHE (2025-06-11 13:41:05 -0400) ---------------------------------------------------------------- Current exclusion rules for ->d_flags stores are rather unpleasant. The basic rules are simple: * stores to dentry->d_flags are OK under dentry->d_lock. * stores to dentry->d_flags are OK in the dentry constructor, before becomes potentially visible to other threads. Unfortunately, there's a couple of exceptions to that, and that's where the headache comes from. Main PITA comes from d_set_d_op(); that primitive sets ->d_op of dentry and adjusts the flags that correspond to presence of individual methods. It's very easy to misuse; existing uses _are_ safe, but proof of correctness is brittle. Use in __d_alloc() is safe (we are within a constructor), but we might as well precalculate the initial value of ->d_flags when we set the default ->d_op for given superblock and set ->d_flags directly instead of messing with that helper. The reasons why other uses are safe are bloody convoluted; I'm not going to reproduce it here. See https://lore.kernel.org/all/20250224010624.GT1977892@ZenIV/ for gory details, if you care. The critical part is using d_set_d_op() only just prior to d_splice_alias(), which makes a combination of d_splice_alias() with setting ->d_op, etc. a natural replacement primitive. Better yet, if we go that way, it's easy to take setting ->d_op and modifying ->d_flags under ->d_lock, which eliminates the headache as far as ->d_flags exclusion rules are concerned. Other exceptions are minor and easy to deal with. What this series does: * d_set_d_op() is no longer available; new primitive (d_splice_alias_ops()) is provided, equivalent to combination of d_set_d_op() and d_splice_alias(). * new field of struct super_block - ->s_d_flags. Default value of ->d_flags to be used when allocating dentries on this filesystem. * new primitive for setting ->s_d_op: set_default_d_op(). Replaces stores to ->s_d_op at mount time. All in-tree filesystems converted; out-of-tree ones will get caught by compiler (->s_d_op is renamed, so stores to it will be caught). ->s_d_flags is set by the same primitive to match the ->s_d_op. * a lot of filesystems had ->s_d_op->d_delete equal to always_delete_dentry; that is equivalent to setting DCACHE_DONTCACHE in ->d_flags, so such filesystems can bloody well set that bit in ->s_d_flags and drop ->d_delete() from dentry_operations. In quite a few cases that results in empty dentry_operations, which means that we can get rid of those. * kill simple_dentry_operations - not needed anymore. * massage d_alloc_parallel() to get rid of the other exception wrt ->d_flags stores - we can set DCACHE_PAR_LOOKUP as soon as we allocate the new dentry; no need to delay that until we commit to using the sucker. As the result, ->d_flags stores are all either under ->d_lock or done before the dentry becomes visible in any shared data structures. ---------------------------------------------------------------- Al Viro (20): d_set_mounted(): we don't need to bump seqcount component of rename_lock procfs: kill ->proc_dops new helper: d_splice_alias_ops() switch procfs from d_set_d_op() to d_splice_alias_ops() fuse: no need for special dentry_operations for root dentry new helper: set_default_d_op() split d_flags calculation out of d_set_d_op() correct the set of flags forbidden at d_set_d_op() time set_default_d_op(): calculate the matching value for ->d_flags simple_lookup(): just set DCACHE_DONTCACHE make d_set_d_op() static d_alloc_parallel(): set DCACHE_PAR_LOOKUP earlier shmem: no dentry retention past the refcount reaching zero devpts, sunrpc, hostfs: don't bother with ->d_op kill simple_dentry_operations ramfs, hugetlbfs, mqueue: set DCACHE_DONTCACHE 9p: don't bother with always_delete_dentry efivarfs: use DCACHE_DONTCACHE instead of always_delete_dentry() debugfs: use DCACHE_DONTCACHE configfs: use DCACHE_DONTCACHE Steven Rostedt (1): tracefs: Add d_delete to remove negative dentries Documentation/filesystems/porting.rst | 18 ++++ fs/9p/vfs_dentry.c | 1 - fs/9p/vfs_super.c | 10 ++- fs/adfs/super.c | 2 +- fs/affs/super.c | 4 +- fs/afs/super.c | 4 +- fs/autofs/inode.c | 2 +- fs/btrfs/super.c | 2 +- fs/ceph/super.c | 2 +- fs/coda/inode.c | 2 +- fs/configfs/dir.c | 1 - fs/configfs/mount.c | 3 +- fs/dcache.c | 153 ++++++++++++++++++++-------------- fs/debugfs/inode.c | 4 +- fs/devpts/inode.c | 2 +- fs/ecryptfs/main.c | 2 +- fs/efivarfs/super.c | 4 +- fs/exfat/super.c | 4 +- fs/fat/namei_msdos.c | 2 +- fs/fat/namei_vfat.c | 4 +- fs/fuse/dir.c | 7 -- fs/fuse/fuse_i.h | 1 - fs/fuse/inode.c | 6 +- fs/gfs2/ops_fstype.c | 2 +- fs/hfs/super.c | 2 +- fs/hfsplus/super.c | 2 +- fs/hostfs/hostfs_kern.c | 2 +- fs/hpfs/super.c | 2 +- fs/hugetlbfs/inode.c | 1 + fs/isofs/inode.c | 2 +- fs/jfs/super.c | 2 +- fs/kernfs/mount.c | 2 +- fs/libfs.c | 27 +++--- fs/nfs/super.c | 2 +- fs/ntfs3/super.c | 3 +- fs/ocfs2/super.c | 2 +- fs/orangefs/super.c | 2 +- fs/overlayfs/super.c | 2 +- fs/proc/base.c | 9 +- fs/proc/generic.c | 10 ++- fs/proc/internal.h | 6 +- fs/proc/namespaces.c | 3 +- fs/proc/proc_sysctl.c | 7 +- fs/ramfs/inode.c | 1 + fs/smb/client/cifsfs.c | 4 +- fs/tracefs/inode.c | 13 ++- fs/vboxsf/super.c | 2 +- include/linux/dcache.h | 6 +- include/linux/fs.h | 4 +- include/linux/proc_fs.h | 2 + ipc/mqueue.c | 1 + mm/shmem.c | 4 +- net/sunrpc/rpc_pipe.c | 2 +- 53 files changed, 210 insertions(+), 159 deletions(-)
