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dcache: add extra sanity checks of the dentry in dentry_free()

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If d_flags isn't what we expect, then it's good to display it. Add a new
DENTRY_WARN_ONCE() macro that also displays d_flags for the dentry.
Change D_FLAG_VERIFY() to call that instead of a generic WARN_ON_ONCE().

Change the existing hlist_unhashed() check in dentry_free() to use the
new macro, and add checks for other invariants of a dead dentry. Notably:

1) Ensure that DCACHE_LRU_LIST and DCACHE_SHRINK_LIST are not set.

2) Ensure that d_lockref is negative

Signed-off-by: Jeff Layton <jlayton@kernel.org>
Link: https://patch.msgid.link/20260422-dcache-warn-v1-1-50155e1b40b6@kernel.org
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
This commit is contained in:
Jeff Layton 2026-04-22 07:29:48 -04:00 committed by Christian Brauner
parent 9f93417af4
commit c06d4e760c
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1 changed files with 8 additions and 2 deletions
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10
fs/dcache.c
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@ -426,9 +426,16 @@ static inline void __d_clear_type_and_inode(struct dentry *dentry)
this_cpu_inc(nr_dentry_negative);
}
#define DENTRY_WARN_ONCE(condition, dentry) \
WARN_ONCE((condition), "dentry=%p d_flags=0x%x\n", (dentry), (dentry)->d_flags)
#define D_FLAG_VERIFY(dentry, x) \
DENTRY_WARN_ONCE(((dentry)->d_flags & (DCACHE_LRU_LIST | DCACHE_SHRINK_LIST)) != (x), (dentry))
static void dentry_free(struct dentry *dentry)
{
WARN_ON(d_really_is_positive(dentry));
DENTRY_WARN_ONCE(d_really_is_positive(dentry), dentry);
DENTRY_WARN_ONCE(dentry->d_lockref.count >= 0, dentry);
D_FLAG_VERIFY(dentry, 0);
if (unlikely(dname_external(dentry))) {
struct external_name *p = external_name(dentry);
if (likely(atomic_dec_and_test(&p->count))) {
@ -495,7 +502,6 @@ static void dentry_unlink_inode(struct dentry * dentry)
* These helper functions make sure we always follow the
* rules. d_lock must be held by the caller.
*/
#define D_FLAG_VERIFY(dentry,x) WARN_ON_ONCE(((dentry)->d_flags & (DCACHE_LRU_LIST | DCACHE_SHRINK_LIST)) != (x))
static void d_lru_add(struct dentry *dentry)
{
D_FLAG_VERIFY(dentry, 0);