dcache: convert dentry flag macros to enum

Commit 9748cb2dc393 ("VFS: repack DENTRY_ flags.") changed the value of
DCACHE_MOUNTED, which broke drgn's path_lookup() helper. drgn is forced
to hard-cod

dcache: convert dentry flag macros to enum

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 <[email protected]>
Link: https://lore.kernel.org/177665a082f048cf536b9cd6af467b3be6b6e6ed.1744141838.git.osandov@fb.com
Signed-off-by: Christian Brauner <[email protected]>

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nfs/vfs: discard d_exact_alias()

d_exact_alias() is a descendent of d_add_unique() which was introduced
20 years ago mostly likely to work around problems with NFS servers of
the time. It is now no

nfs/vfs: discard d_exact_alias()

d_exact_alias() is a descendent of d_add_unique() which was introduced
20 years ago mostly likely to work around problems with NFS servers of
the time. It is now not used in several situations were it was
originally needed and there have been no reports of problems -
presumably the old NFS servers have been improved. This only place it
is now use is in NFSv4 code and the old problematic servers are thought
to have been v2/v3 only.

There is no clear benefit in reusing a unhashed() dentry which happens
to have the same name as the dentry we are adding.

So this patch removes d_exact_alias() and the one place that it is used.

Cc: Trond Myklebust <[email protected]>
Signed-off-by: NeilBrown <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Christian Brauner <[email protected]>

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VFS: repack DENTRY_ flags.

Bits 13, 23, 24, and 27 are not used. Move all those holes to the end.

Signed-off-by: NeilBrown <[email protected]>
Link: https://lore.kernel.org/r/20250206054504.2950516-7-

VFS: repack DENTRY_ flags.

Bits 13, 23, 24, and 27 are not used. Move all those holes to the end.

Signed-off-by: NeilBrown <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Christian Brauner <[email protected]>

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fs: dcache: move the sysctl to fs/dcache.c

The sysctl_vfs_cache_pressure belongs to fs/dcache.c, move it to
fs/dcache.c from kernel/sysctl.c. As a part of fs/dcache.c cleaning,
sysctl_vfs_cache_pres

fs: dcache: move the sysctl to fs/dcache.c

The sysctl_vfs_cache_pressure belongs to fs/dcache.c, move it to
fs/dcache.c from kernel/sysctl.c. As a part of fs/dcache.c cleaning,
sysctl_vfs_cache_pressure is changed to a static variable, and change
the inline-type function vfs_pressure_ratio() to out-of-inline type,
export vfs_pressure_ratio() with EXPORT_SYMBOL_GPL to be used by other
files. Move the unneeded include(linux/dcache.h).

Signed-off-by: Kaixiong Yu <[email protected]>
Reviewed-by: Kees Cook <[email protected]>
Reviewed-by: Jan Kara <[email protected]>
Reviewed-by: Christian Brauner <[email protected]>
Reviewed-by: Jeff Layton <[email protected]>
Signed-off-by: Joel Granados <[email protected]>

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add a string-to-qstr constructor

Quite a few places want to build a struct qstr by given string;
it would be convenient to have a primitive doing that, rather
than open-coding it via QSTR_INIT().

T

add a string-to-qstr constructor

Quite a few places want to build a struct qstr by given string;
it would be convenient to have a primitive doing that, rather
than open-coding it via QSTR_INIT().

The closest approximation was in bcachefs, but that expands to
initializer list - {.len = strlen(string), .name = string}.
It would be more useful to have it as compound literal -
(struct qstr){.len = strlen(string), .name = string}.

Unlike initializer list it's a valid expression. What's more,
it's a valid lvalue - it's an equivalent of anonymous local
variable with such initializer, so the things like
path->dentry = d_alloc_pseudo(mnt->mnt_sb, &QSTR(name));
are valid. It can also be used as initializer, with identical
effect -
struct qstr x = (struct qstr){.name = s, .len = strlen(s)};
is equivalent to
struct qstr anon_variable = {.name = s, .len = strlen(s)};
struct qstr x = anon_variable;
// anon_variable is never used after that point
and any even remotely sane compiler will manage to collapse that
into
struct qstr x = {.name = s, .len = strlen(s)};

What compound literals can't be used for is initialization of
global variables, but those are covered by QSTR_INIT().

This commit lifts definition(s) of QSTR() into linux/dcache.h,
converts it to compound literal (all bcachefs users are fine
with that) and converts assorted open-coded instances to using
that.

Signed-off-by: Al Viro <[email protected]>

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9p: fix ->rename_sem exclusion

9p wants to be able to build a path from given dentry to fs root and keep
it valid over a blocking operation.

->s_vfs_rename_mutex would be a natural candidate, but t

9p: fix ->rename_sem exclusion

9p wants to be able to build a path from given dentry to fs root and keep
it valid over a blocking operation.

->s_vfs_rename_mutex would be a natural candidate, but there are places
where we need that and where we have no way to tell if ->s_vfs_rename_mutex
is already held deeper in callchain. Moreover, it's only held for
cross-directory renames; name changes within the same directory happen
without it.

Solution:
* have d_move() done in ->rename() rather than in its caller
* maintain a 9p-private rwsem (per-filesystem)
* hold it exclusive over the relevant part of ->rename()
* hold it shared over the places where we want the path.

That almost works. FS_RENAME_DOES_D_MOVE is enough to put all d_move()
and d_exchange() calls under filesystem's control. However, there's
also __d_unalias(), which isn't covered by any of that.

If ->lookup() hits a directory inode with preexisting dentry elsewhere
(due to e.g. rename done on server behind our back), d_splice_alias()
called by ->lookup() will move/rename that alias.

Add a couple of optional methods, so that __d_unalias() would do
if alias->d_op->d_unalias_trylock != NULL
if (!alias->d_op->d_unalias_trylock(alias))
fail (resulting in -ESTALE from lookup)
__d_move(...)
if alias->d_op->d_unalias_unlock != NULL
alias->d_unalias_unlock(alias)
where it currently does __d_move(). 9p instances do down_write_trylock()
and up_write() of ->rename_mutex.

Signed-off-by: Al Viro <[email protected]>

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Pass parent directory inode and expected name to ->d_revalidate()

->d_revalidate() often needs to access dentry parent and name; that has
to be done carefully, since the locking environment varies f

Pass parent directory inode and expected name to ->d_revalidate()

->d_revalidate() often needs to access dentry parent and name; that has
to be done carefully, since the locking environment varies from caller
to caller. We are not guaranteed that dentry in question will not be
moved right under us - not unless the filesystem is such that nothing
on it ever gets renamed.

It can be dealt with, but that results in boilerplate code that isn't
even needed - the callers normally have just found the dentry via dcache
lookup and want to verify that it's in the right place; they already
have the values of ->d_parent and ->d_name stable. There is a couple
of exceptions (overlayfs and, to less extent, ecryptfs), but for the
majority of calls that song and dance is not needed at all.

It's easier to make ecryptfs and overlayfs find and pass those values if
there's a ->d_revalidate() instance to be called, rather than doing that
in the instances.

This commit only changes the calling conventions; making use of supplied
values is left to followups.

NOTE: some instances need more than just the parent - things like CIFS
may need to build an entire path from filesystem root, so they need
more precautions than the usual boilerplate. This series doesn't
do anything to that need - these filesystems have to keep their locking
mechanisms (rename_lock loops, use of dentry_path_raw(), private rwsem
a-la v9fs).

One thing to keep in mind when using name is that name->name will normally
point into the pathname being resolved; the filename in question occupies
name->len bytes starting at name->name, and there is NUL somewhere after it,
but it the next byte might very well be '/' rather than '\0'. Do not
ignore name->len.

Reviewed-by: Jeff Layton <[email protected]>
Reviewed-by: Gabriel Krisman Bertazi <[email protected]>
Signed-off-by: Al Viro <[email protected]>

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dcache: back inline names with a struct-wrapped array of unsigned long

... so that they can be copied with struct assignment (which generates
better code) and accessed word-by-word.

The type is uni

dcache: back inline names with a struct-wrapped array of unsigned long

... so that they can be copied with struct assignment (which generates
better code) and accessed word-by-word.

The type is union shortname_storage; it's a union of arrays of
unsigned char and unsigned long.

struct name_snapshot.inline_name turned into union shortname_storage;
users (all in fs/dcache.c) adjusted.

struct dentry.d_iname has some users outside of fs/dcache.c; to
reduce the amount of noise in commit, it is replaced with
union shortname_storage d_shortname and d_iname is turned into a macro
that expands to d_shortname.string (similar to d_lock handling).
That compat macro is temporary - most of the remaining instances will
be taken out by debugfs series, and once that is merged and few others
are taken care of this will go away.

Reviewed-by: Jeff Layton <[email protected]>
Reviewed-by: Jan Kara <[email protected]>
Signed-off-by: Al Viro <[email protected]>

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make sure that DNAME_INLINE_LEN is a multiple of word size

... calling the number of words DNAME_INLINE_WORDS.

The next step will be to have a structure to hold inline name arrays
(both in dentry a

make sure that DNAME_INLINE_LEN is a multiple of word size

... calling the number of words DNAME_INLINE_WORDS.

The next step will be to have a structure to hold inline name arrays
(both in dentry and in name_snapshot) and use that to alias the
existing arrays of unsigned char there. That will allow both
full-structure copies and convenient word-by-word accesses.

Reviewed-by: Jeff Layton <[email protected]>
Reviewed-by: Jan Kara <[email protected]>
Signed-off-by: Al Viro <[email protected]>

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fs: fix dentry size

On CONFIG_SMP=y and on 32bit we need to decrease DNAME_INLINE_LEN to 36
btyes to end up with 128 bytes in total.

Reported-by: Linus Torvalds <[email protected]>
Link

fs: fix dentry size

On CONFIG_SMP=y and on 32bit we need to decrease DNAME_INLINE_LEN to 36
btyes to end up with 128 bytes in total.

Reported-by: Linus Torvalds <[email protected]>
Links: https://lore.kernel.org/r/CAHk-=whtoqTSCcAvV-X-KPqoDWxS4vxmWpuKLB+Vv8=FtUd5vA@mail.gmail.com
Signed-off-by: Christian Brauner <[email protected]>

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vfs: move d_lockref out of the area used by RCU lookup

Stock kernel scales worse than FreeBSD when doing a 20-way stat(2) on
the same tmpfs-backed file.

According to perf top:
38.09% lockref_put

vfs: move d_lockref out of the area used by RCU lookup

Stock kernel scales worse than FreeBSD when doing a 20-way stat(2) on
the same tmpfs-backed file.

According to perf top:
38.09% lockref_put_return
26.08% lockref_get_not_dead
25.60% __d_lookup_rcu
0.89% clear_bhb_loop

__d_lookup_rcu is participating in cacheline ping pong due to the
embedded name sharing a cacheline with lockref.

Moving it out resolves the problem:
41.50% lockref_put_return
41.03% lockref_get_not_dead
1.54% clear_bhb_loop

benchmark (will-it-scale, Sapphire Rapids, tmpfs, ops/s):
FreeBSD:7219334
before: 5038006
after: 7842883 (+55%)

One minor remark: the 'after' result is unstable, fluctuating in the
range ~7.8 mln to ~9 mln during different runs.

Signed-off-by: Mateusz Guzik <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Christian Brauner <[email protected]>

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vfs: rename parent_ino to d_parent_ino and make it use RCU

The routine is used by procfs through dir_emit_dots.

The combined RCU and lock fallback implementation is too big for an
inline. Given tha

vfs: rename parent_ino to d_parent_ino and make it use RCU

The routine is used by procfs through dir_emit_dots.

The combined RCU and lock fallback implementation is too big for an
inline. Given that the routine takes a dentry argument fs/dcache.c seems
like the place to put it in.

Signed-off-by: Mateusz Guzik <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Christian Brauner <[email protected]>

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Revert "get rid of DCACHE_GENOCIDE"

This reverts commit 57851607326a2beef21e67f83f4f53a90df8445a.

Unfortunately, while we only call that thing once, the callback
*can* be called more than once for

Revert "get rid of DCACHE_GENOCIDE"

This reverts commit 57851607326a2beef21e67f83f4f53a90df8445a.

Unfortunately, while we only call that thing once, the callback
*can* be called more than once for the same dentry - all it
takes is rename_lock being touched while we are in d_walk().
For now let's revert it.

Signed-off-by: Al Viro <[email protected]>

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fs: remove the inode argument to ->d_real() method

The only remaining user of ->d_real() method is d_real_inode(), which
passed NULL inode argument to get the real data dentry.

There are no longer

fs: remove the inode argument to ->d_real() method

The only remaining user of ->d_real() method is d_real_inode(), which
passed NULL inode argument to get the real data dentry.

There are no longer any users that call ->d_real() with a non-NULL
inode argument for getting a detry from a specific underlying layer.

Remove the inode argument of the method and replace it with an integer
'type' argument, to allow callers to request the real metadata dentry
instead of the real data dentry.

All the current users of d_real_inode() (e.g. uprobe) continue to get
the real data inode. Caller that need to get the real metadata inode
(e.g. IMA/EVM) can use d_inode(d_real(dentry, D_REAL_METADATA)).

Signed-off-by: Amir Goldstein <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Tested-by: Stefan Berger <[email protected]>
Signed-off-by: Al Viro <[email protected]>
Signed-off-by: Christian Brauner <[email protected]>

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dcache: remove unnecessary NULL check in dget_dlock()

dget_dlock() requires dentry->d_lock to be held when called, yet
contains a NULL check for dentry.

An audit of all calls to dget_dlock() shows

dcache: remove unnecessary NULL check in dget_dlock()

dget_dlock() requires dentry->d_lock to be held when called, yet
contains a NULL check for dentry.

An audit of all calls to dget_dlock() shows that it is never called
with a NULL pointer (as spin_lock()/spin_unlock() would crash in these
cases):

$ git grep -W '\<dget_dlock\>'

arch/powerpc/platforms/cell/spufs/inode.c- spin_lock(&dentry->d_lock);
arch/powerpc/platforms/cell/spufs/inode.c- if (simple_positive(dentry)) {
arch/powerpc/platforms/cell/spufs/inode.c: dget_dlock(dentry);

fs/autofs/expire.c- spin_lock_nested(&child->d_lock, DENTRY_D_LOCK_NESTED);
fs/autofs/expire.c- if (simple_positive(child)) {
fs/autofs/expire.c: dget_dlock(child);

fs/autofs/root.c: dget_dlock(active);
fs/autofs/root.c- spin_unlock(&active->d_lock);

fs/autofs/root.c: dget_dlock(expiring);
fs/autofs/root.c- spin_unlock(&expiring->d_lock);

fs/ceph/dir.c- if (!spin_trylock(&dentry->d_lock))
fs/ceph/dir.c- continue;
[...]
fs/ceph/dir.c: dget_dlock(dentry);

fs/ceph/mds_client.c- spin_lock(&alias->d_lock);
[...]
fs/ceph/mds_client.c: dn = dget_dlock(alias);

fs/configfs/inode.c- spin_lock(&dentry->d_lock);
fs/configfs/inode.c- if (simple_positive(dentry)) {
fs/configfs/inode.c: dget_dlock(dentry);

fs/libfs.c: found = dget_dlock(d);
fs/libfs.c- spin_unlock(&d->d_lock);

fs/libfs.c: found = dget_dlock(child);
fs/libfs.c- spin_unlock(&child->d_lock);

fs/libfs.c: child = dget_dlock(d);
fs/libfs.c- spin_unlock(&d->d_lock);

fs/ocfs2/dcache.c: dget_dlock(dentry);
fs/ocfs2/dcache.c- spin_unlock(&dentry->d_lock);

include/linux/dcache.h:static inline struct dentry *dget_dlock(struct dentry *dentry)

After taking out the NULL check, dget_dlock() becomes almost identical
to __dget_dlock(); the only difference is that dget_dlock() returns the
dentry that was passed in. These are static inline helpers, so we can
rely on the compiler to discard unused return values. We can therefore
also remove __dget_dlock() and replace calls to it by dget_dlock().

Also fix up and improve the kerneldoc comments while we're at it.

Al Viro pointed out that we can also clean up some of the callers to
make use of the returned value and provided a bit more info for the
kerneldoc.

While preparing v2 I also noticed that the tabs used in the kerneldoc
comments were causing the kerneldoc to get parsed incorrectly so I also
fixed this up (including for d_unhashed, which is otherwise unrelated).

Testing: x86 defconfig build + boot; make htmldocs for the kerneldoc
warning. objdump shows there are code generation changes.

Link: https://lore.kernel.org/all/[email protected]/
Cc: Alexander Viro <[email protected]>
Cc: Christian Brauner <[email protected]>
Cc: [email protected]
Cc: Nick Piggin <[email protected]>
Cc: Waiman Long <[email protected]>
Cc: [email protected]
Signed-off-by: Vegard Nossum <[email protected]>
Signed-off-by: Al Viro <[email protected]>

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kill DCACHE_MAY_FREE

With the new ordering in __dentry_kill() it has become redundant -
it's set if and only if both DCACHE_DENTRY_KILLED and DCACHE_SHRINK_LIST
are set.

We set it in __dentry_kill(

kill DCACHE_MAY_FREE

With the new ordering in __dentry_kill() it has become redundant -
it's set if and only if both DCACHE_DENTRY_KILLED and DCACHE_SHRINK_LIST
are set.

We set it in __dentry_kill(), after having set DCACHE_DENTRY_KILLED
with the only condition being that DCACHE_SHRINK_LIST is there;
all of that is done without dropping ->d_lock and the only place
that checks that flag (shrink_dentry_list()) does so under ->d_lock,
after having found the victim on its shrink list. Since DCACHE_SHRINK_LIST
is set only when placing dentry into shrink list and removed only by
shrink_dentry_list() itself, a check for DCACHE_DENTRY_KILLED in
there would be equivalent to check for DCACHE_MAY_FREE.

Signed-off-by: Al Viro <[email protected]>

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get rid of DCACHE_GENOCIDE

... now that we never call d_genocide() other than from kill_litter_super()

Signed-off-by: Al Viro <[email protected]>

d_genocide(): move the extern into fs/internal.h

Signed-off-by: Al Viro <[email protected]>

kill d_instantate_anon(), fold __d_instantiate_anon() into remaining caller

now that the only user of d_instantiate_anon() is gone...
[braino fix folded - kudos to Dan Carpenter]

Signed-off-by: Al

kill d_instantate_anon(), fold __d_instantiate_anon() into remaining caller

now that the only user of d_instantiate_anon() is gone...
[braino fix folded - kudos to Dan Carpenter]

Signed-off-by: Al Viro <[email protected]>

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dentry: switch the lists of children to hlist

Saves a pointer per struct dentry and actually makes the things less
clumsy. Cleaned the d_walk() and dcache_readdir() a bit by use
of hlist_for_... it

dentry: switch the lists of children to hlist

Saves a pointer per struct dentry and actually makes the things less
clumsy. Cleaned the d_walk() and dcache_readdir() a bit by use
of hlist_for_... iterators.

A couple of new helpers - d_first_child() and d_next_sibling(),
to make the expressions less awful.

Reviewed-by: Christian Brauner <[email protected]>
Signed-off-by: Al Viro <[email protected]>

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kill d_backing_dentry()

no users left

Signed-off-by: Al Viro <[email protected]>

[software coproarchaeology] dentry.h: kill a mysterious comment

there's a strange comment in front of d_lookup() declaration:

/* appendix may either be NULL or be used for transname suffixes */

Lo

[software coproarchaeology] dentry.h: kill a mysterious comment

there's a strange comment in front of d_lookup() declaration:

/* appendix may either be NULL or be used for transname suffixes */

Looks like nobody had been curious enough to track its history;
it predates git, it predates bitkeeper and if you look through
the pre-BK trees, you finally arrive at this in 2.1.44-for-davem:
/* appendix may either be NULL or be used for transname suffixes */
-extern struct dentry * d_lookup(struct inode * dir, struct qstr * name,
- struct qstr * appendix);
+extern struct dentry * d_lookup(struct dentry * dir, struct qstr * name);
In other words, it refers to the third argument d_lookup() used to have
back then. It had been introduced in 2.1.43-pre, on June 12 1997,
along with d_lookup(), only to be removed by July 4 1997, presumably
when the Cthulhu-awful thing it used to be used for (look for
CONFIG_TRANS_NAMES in 2.1.43-pre, and keep a heavy-duty barfbag
ready) had been, er, noticed and recognized for what it had been.

Despite the appendectomy, the comment remained. Some things really
need to be put out of their misery...

Signed-off-by: Al Viro <[email protected]>

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dentry.h: trim externs

d_instantiate_unique() had been gone for 7 years; __d_lookup...()
and shrink_dcache_for_umount() are fs/internal.h fodder.

Signed-off-by: Al Viro <[email protected]>

kill d_{is,set}_fallthru()

Introduced in 2015 and never had any in-tree users...

Signed-off-by: Al Viro <[email protected]>

DCACHE_COOKIE: RIP

the last user gone in 2021...

Signed-off-by: Al Viro <[email protected]>