[patch 04/19] LOCKD: Fix a deadlock in nlm_traverse_files()

[Greg KH <gregkh@suse.de>]

-stable review patch.  If anyone has any objections, please let us know.

------------------
From: Trond Myklebust <Trond.Myklebust@netapp.com>

nlm_traverse_files() is not allowed to hold the nlm_file_mutex while calling
nlm_inspect file, since it may end up calling nlm_release_file() when
releaseing the blocks.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
 fs/lockd/svcsubs.c |   15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

--- linux-2.6.17.13.orig/fs/lockd/svcsubs.c
+++ linux-2.6.17.13/fs/lockd/svcsubs.c
@@ -238,19 +238,22 @@ static int
 nlm_traverse_files(struct nlm_host *host, int action)
 {
 	struct nlm_file	*file, **fp;
-	int		i;
+	int i, ret = 0;
 
 	mutex_lock(&nlm_file_mutex);
 	for (i = 0; i < FILE_NRHASH; i++) {
 		fp = nlm_files + i;
 		while ((file = *fp) != NULL) {
+			file->f_count++;
+			mutex_unlock(&nlm_file_mutex);
+
 			/* Traverse locks, blocks and shares of this file
 			 * and update file->f_locks count */
-			if (nlm_inspect_file(host, file, action)) {
-				mutex_unlock(&nlm_file_mutex);
-				return 1;
-			}
+			if (nlm_inspect_file(host, file, action))
+				ret = 1;
 
+			mutex_lock(&nlm_file_mutex);
+			file->f_count--;
 			/* No more references to this file. Let go of it. */
 			if (!file->f_blocks && !file->f_locks
 			 && !file->f_shares && !file->f_count) {
@@ -263,7 +266,7 @@ nlm_traverse_files(struct nlm_host *host
 		}
 	}
 	mutex_unlock(&nlm_file_mutex);
-	return 0;
+	return ret;
 }
 
 /*

--
-
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