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__dentry_kill(): get consistent rules for victim's refcount

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Currently we call it with refcount equal to 1 when called from
dentry_kill(); all other callers have it equal to 0.

Make it always be called with zero refcount; on this step we
just decrement it before the calls in dentry_kill().  That is
safe, since all places that care about the value of refcount
either do that under ->d_lock or hold a reference to dentry
in question.  Either is sufficient to prevent observing a
dentry immediately prior to __dentry_kill() getting called
from dentry_kill().

Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2023-10-29 18:38:27 -04:00
parent e9d130d050
commit ee0c82503d
1 changed files with 2 additions and 0 deletions
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2
fs/dcache.c
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@ -729,6 +729,7 @@ static struct dentry *dentry_kill(struct dentry *dentry)
goto slow_positive;
}
}
dentry->d_lockref.count--;
__dentry_kill(dentry);
return parent;
@ -741,6 +742,7 @@ static struct dentry *dentry_kill(struct dentry *dentry)
if (unlikely(dentry->d_lockref.count != 1)) {
dentry->d_lockref.count--;
} else if (likely(!retain_dentry(dentry))) {
dentry->d_lockref.count--;
__dentry_kill(dentry);
return parent;
} else {