| Message ID | 20231109062056.3181775-13-viro@zeniv.linux.org.uk (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [01/22] struct dentry: get rid of randomize_layout idiocy | expand |
On Thu, Nov 09, 2023 at 06:20:47AM +0000, Al Viro wrote: > 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 Also worth noting that dentry_kill() is marked with __releases(dentry->d_lock). I'm usually pretty liberal with lockdep_assert asserts as well because it gives nice splats on testing kernels and makes for much faster review because the assumptions are visible directly in the helper. > in question. Either is sufficient to prevent observing a > dentry immediately prior to __dentry_kill() getting called > from dentry_kill(). > > Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> > --- Looks good to me, Reviewed-by: Christian Brauner <brauner@kernel.org>
diff --git a/fs/dcache.c b/fs/dcache.c index 1f61a5d03d5b..d9466cab4884 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -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 {
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(). Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> --- fs/dcache.c | 2 ++ 1 file changed, 2 insertions(+)