kernel/linux.git/include/linux/dcache.h, branch v6.18.21

make it easier to catch those who try to modify ->d_name

2025-09-16T01:08:33+00:00

Turn d_name into an anon union of const struct qstr d_name with struct qstr __d_name. Very few places need to modify it (all in fs/dcache.c); those are switched to use of ->__d_name. Note that ->d_name can actually change under you unless you have the right locking environment; this const just prohibits accidentally doing stores without being easily spotted. Reviewed-by: Christian Brauner Signed-off-by: Al Viro

make d_set_d_op() static

2025-06-11T17:39:52+00:00

Convert the last user (d_alloc_pseudo()) and be done with that. Any out-of-tree filesystem using it should switch to d_splice_alias_ops() or, better yet, check whether it really needs to have ->d_op vary among its dentries. Reviewed-by: Christian Brauner Signed-off-by: Al Viro

new helper: set_default_d_op()

2025-06-11T02:21:16+00:00

... to be used instead of manually assigning to ->s_d_op. All in-tree filesystem converted (and field itself is renamed, so any out-of-tree ones in need of conversion will be caught by compiler). Reviewed-by: Christian Brauner Signed-off-by: Al Viro

new helper: d_splice_alias_ops()

2025-06-11T02:11:39+00:00

Uses of d_set_d_op() on live dentry can be very dangerous; it is going to be withdrawn and replaced with saner things. The best way for a filesystem is to have the default dentry_operations set at mount time and be done with that - __d_alloc() will use that. Currently there are two cases when d_set_d_op() is used on a live dentry - one is procfs, which has several genuinely different dentry_operations instances (different ->d_revalidate(), etc.) and another is simple_lookup(), where we would be better off without overriding ->d_op. For procfs we have d_set_d_op() calls followed by d_splice_alias(); provide a new helper (d_splice_alias_ops(inode, dentry, d_ops)) that would combine those two, and do the d_set_d_op() part while under ->d_lock. That eliminates one of the places where ->d_flags had been modified without holding ->d_lock; current behaviour is not racy, but the reasons for that are far too brittle. Better move to uniform locking rules and simpler proof of correctness... The next commit will convert procfs to use of that helper; it is not exported and won't be until somebody comes up with convincing modular user for it. Again, the best approach is to have default ->d_op and let __d_alloc() do the right thing; filesystem _may_ need non-uniform ->d_op (procfs does), but there'd better be good reasons for that. Reviewed-by: Christian Brauner Signed-off-by: Al Viro

Merge tag 'vfs-6.16-rc1.async.dir' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

2025-05-26T15:02:43+00:00

Pull vfs directory lookup updates from Christian Brauner: "This contains cleanups for the lookup_one*() family of helpers. We expose a set of functions with names containing "lookup_one_len" and others without the "_len". This difference has nothing to do with "len". It's rater a historical accident that can be confusing. The functions without "_len" take a "mnt_idmap" pointer. This is found in the "vfsmount" and that is an important question when choosing which to use: do you have a vfsmount, or are you "inside" the filesystem. A related question is "is permission checking relevant here?". nfsd and cachefiles *do* have a vfsmount but *don't* use the non-_len functions. They pass nop_mnt_idmap and refuse to work on filesystems which have any other idmap. This work changes nfsd and cachefile to use the lookup_one family of functions and to explictily pass &nop_mnt_idmap which is consistent with all other vfs interfaces used where &nop_mnt_idmap is explicitly passed. The remaining uses of the "_one" functions do not require permission checks so these are renamed to be "_noperm" and the permission checking is removed. This series also changes these lookup function to take a qstr instead of separate name and len. In many cases this simplifies the call" * tag 'vfs-6.16-rc1.async.dir' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: VFS: change lookup_one_common and lookup_noperm_common to take a qstr Use try_lookup_noperm() instead of d_hash_and_lookup() outside of VFS VFS: rename lookup_one_len family to lookup_noperm and remove permission check cachefiles: Use lookup_one() rather than lookup_one_len() nfsd: Use lookup_one() rather than lookup_one_len() VFS: improve interface for lookup_one functions

dcache: convert dentry flag macros to enum

2025-04-11T13:24:29+00:00

Commit 9748cb2dc393 ("VFS: repack DENTRY_ flags.") changed the value of DCACHE_MOUNTED, which broke drgn's path_lookup() helper. drgn is forced to hard-code it because it's a macro, and macros aren't preserved in debugging information by default. Enums, on the other hand, are included in debugging information. Convert the DCACHE_* flag macros to an enum so that debugging tools like drgn and bpftrace can make use of them. Link: https://github.com/osandov/drgn/blob/2027d0fea84d74b835e77392f7040c2a333180c6/drgn/helpers/linux/fs.py#L43-L46 Signed-off-by: Omar Sandoval Link: https://lore.kernel.org/177665a082f048cf536b9cd6af467b3be6b6e6ed.1744141838.git.osandov@fb.com Signed-off-by: Christian Brauner

Use try_lookup_noperm() instead of d_hash_and_lookup() outside of VFS

2025-04-08T09:24:41+00:00

try_lookup_noperm() and d_hash_and_lookup() are nearly identical. The former does some validation of the name where the latter doesn't. Outside of the VFS that validation is likely valuable, and having only one exported function for this task is certainly a good idea. So make d_hash_and_lookup() local to VFS files and change all other callers to try_lookup_noperm(). Note that the arguments are swapped. Signed-off-by: NeilBrown Link: https://lore.kernel.org/r/20250319031545.2999807-6-neil@brown.name Signed-off-by: Christian Brauner

VFS: improve interface for lookup_one functions

2025-04-07T07:25:32+00:00

The family of functions: lookup_one() lookup_one_unlocked() lookup_one_positive_unlocked() appear designed to be used by external clients of the filesystem rather than by filesystems acting on themselves as the lookup_one_len family are used. They are used by: btrfs/ioctl - which is a user-space interface rather than an internal activity exportfs - i.e. from nfsd or the open_by_handle_at interface overlayfs - at access the underlying filesystems smb/server - for file service They should be used by nfsd (more than just the exportfs path) and cachefs but aren't. It would help if the documentation didn't claim they should "not be called by generic code". Also the path component name is passed as "name" and "len" which are (confusingly?) separate by the "base". In some cases the len in simply "strlen" and so passing a qstr using QSTR() would make the calling clearer. Other callers do pass separate name and len which are stored in a struct. Sometimes these are already stored in a qstr, other times it easily could be. So this patch changes these three functions to receive a 'struct qstr *', and improves the documentation. QSTR_LEN() is added to make it easy to pass a QSTR containing a known len. [brauner@kernel.org: take a struct qstr pointer] Signed-off-by: NeilBrown Link: https://lore.kernel.org/r/20250319031545.2999807-2-neil@brown.name Signed-off-by: Christian Brauner

Merge tag 'sysctl-6.15-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/sysctl/sysctl

2025-03-27T04:02:05+00:00

Pull sysctl updates from Joel Granados: - Move vm_table members out of kernel/sysctl.c All vm_table array members have moved to their respective subsystems leading to the removal of vm_table from kernel/sysctl.c. This increases modularity by placing the ctl_tables closer to where they are actually used and at the same time reducing the chances of merge conflicts in kernel/sysctl.c. - ctl_table range fixes Replace the proc_handler function that checks variable ranges in coredump_sysctls and vdso_table with the one that actually uses the extra{1,2} pointers as min/max values. This tightens the range of the values that users can pass into the kernel effectively preventing {under,over}flows. - Misc fixes Correct grammar errors and typos in test messages. Update sysctl files in MAINTAINERS. Constified and removed array size in declaration for alignment_tbl * tag 'sysctl-6.15-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/sysctl/sysctl: (22 commits) selftests/sysctl: fix wording of help messages selftests: fix spelling/grammar errors in sysctl/sysctl.sh MAINTAINERS: Update sysctl file list in MAINTAINERS sysctl: Fix underflow value setting risk in vm_table coredump: Fixes core_pipe_limit sysctl proc_handler sysctl: remove unneeded include sysctl: remove the vm_table sh: vdso: move the sysctl to arch/sh/kernel/vsyscall/vsyscall.c x86: vdso: move the sysctl to arch/x86/entry/vdso/vdso32-setup.c fs: dcache: move the sysctl to fs/dcache.c sunrpc: simplify rpcauth_cache_shrink_count() fs: drop_caches: move sysctl to fs/drop_caches.c fs: fs-writeback: move sysctl to fs/fs-writeback.c mm: nommu: move sysctl to mm/nommu.c security: min_addr: move sysctl to security/min_addr.c mm: mmap: move sysctl to mm/mmap.c mm: util: move sysctls to mm/util.c mm: vmscan: move vmscan sysctls to mm/vmscan.c mm: swap: move sysctl to mm/swap.c mm: filemap: move sysctl to mm/filemap.c ...

Merge patch series "prep patches for my mkdir series"

2025-02-27T08:25:34+00:00

NeilBrown says: These two patches are cleanup are dependencies for my mkdir changes and subsequence directory locking changes. * patches from https://lore.kernel.org/r/20250226062135.2043651-1-neilb@suse.de: (2 commits) nfsd: drop fh_update() from S_IFDIR branch of nfsd_create_locked() nfs/vfs: discard d_exact_alias() Link: https://lore.kernel.org/r/20250226062135.2043651-1-neilb@suse.de Signed-off-by: Christian Brauner