vfs: dcache: use DCACHE_DENTRY_KILLED instead of DCACHE_DISCONNECTED in d_kill() (b161dfa6) · Commits · 戴 / test

IBM reported a soft lockup after applying the fix for the rename_lock deadlock. Commit ("VFS: Fix the nfs sillyrename regression in kernel 2.6.38") was found to be the culprit. The nfs sillyrename fix used DCACHE_DISCONNECTED to indicate that the dentry was killed. This flag can be set on non-killed dentries too, which results in infinite retries when trying to traverse the dentry tree. This patch introduces a separate flag: DCACHE_DENTRY_KILLED, which is only set in d_kill() and makes try_to_ascend() test only this flag. IBM reported successful test results with this patch. Signed-off-by:

Miklos Szeredi <mszeredi@suse.cz> Cc: Trond Myklebust <Trond.Myklebust@netapp.com> Cc: stable@vger.kernel.org Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

fs/dcache.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -389,7 +389,7 @@ static struct dentry d_kill(struct dentry dentry, struct dentry *parent)
		* Inform try_to_ascend() that we are no longer attached to the
		* dentry tree
		*/
		dentry->d_flags \|= DCACHE_DISCONNECTED;
		dentry->d_flags \|= DCACHE_DENTRY_KILLED;
		if (parent)
		spin_unlock(&parent->d_lock);
		dentry_iput(dentry);
		@@ -1048,7 +1048,7 @@ static struct dentry try_to_ascend(struct dentry old, int locked, unsigned seq
		* or deletion
		*/
		if (new != old->d_parent \|\|
		(old->d_flags & DCACHE_DISCONNECTED) \|\|
		(old->d_flags & DCACHE_DENTRY_KILLED) \|\|
		(!locked && read_seqretry(&rename_lock, seq))) {
		spin_unlock(&new->d_lock);
		new = NULL;

include/linux/dcache.h

+2 −0

Original line number	Diff line number	Diff line
		@@ -206,6 +206,8 @@ struct dentry_operations {
		#define DCACHE_MANAGED_DENTRY \
		(DCACHE_MOUNTED\|DCACHE_NEED_AUTOMOUNT\|DCACHE_MANAGE_TRANSIT)

		#define DCACHE_DENTRY_KILLED 0x100000

		extern seqlock_t rename_lock;

		static inline int dname_external(struct dentry *dentry)

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