[PATCH 03/08] dm: fix idr_pre_get lock ordering

[Jeff Mahoney]

 idr_pre_get() can sleep while allocating memory for the worst-case scenario.
 This isn't a huge deal with the current code, but the next patch will
 switch _minor_lock to a spinlock.

Signed-off-by: Jeff Mahoney <jeffm@xxxxxxxx>
--
 drivers/md/dm.c |   20 ++++++++------------
 1 files changed, 8 insertions(+), 12 deletions(-)

diff -ruNpX ../dontdiff linux-2.6.16-staging1/drivers/md/dm.c linux-2.6.16-staging2/drivers/md/dm.c
--- linux-2.6.16-staging1/drivers/md/dm.c	2006-04-13 16:18:17.000000000 -0400
+++ linux-2.6.16-staging2/drivers/md/dm.c	2006-04-13 16:18:17.000000000 -0400
@@ -717,6 +717,10 @@ static int specific_minor(struct mapped_
 	if (minor >= (1 << MINORBITS))
 		return -EINVAL;
 
+	r = idr_pre_get(&_minor_idr, GFP_KERNEL);
+	if (!r)
+		return -ENOMEM;
+
 	down(&_minor_lock);
 
 	if (idr_find(&_minor_idr, minor)) {
@@ -724,12 +728,6 @@ static int specific_minor(struct mapped_
 		goto out;
 	}
 
-	r = idr_pre_get(&_minor_idr, GFP_KERNEL);
-	if (!r) {
-		r = -ENOMEM;
-		goto out;
-	}
-
 	r = idr_get_new_above(&_minor_idr, MINOR_ALLOCED, minor, &m);
 	if (r) {
 		goto out;
@@ -751,13 +749,11 @@ static int next_free_minor(struct mapped
 	int r;
 	unsigned int m;
 
-	down(&_minor_lock);
-
 	r = idr_pre_get(&_minor_idr, GFP_KERNEL);
-	if (!r) {
-		r = -ENOMEM;
-		goto out;
-	}
+	if (!r)
+		return -ENOMEM;
+
+	down(&_minor_lock);
 
 	r = idr_get_new(&_minor_idr, MINOR_ALLOCED, &m);
 	if (r) {
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/