3.16-stable review patch. If anyone has any objections, please let me know.
------------------
From: Weston Andros Adamson <dros@xxxxxxxxxxxxxxx>
commit bc8a309e88a86205fc3e17f06e42a2e56fc6f807 upstream.
nfs_page_group_lock was calling wait_on_bit_lock even when told not to
block. Fix by first trying test_and_set_bit, followed by wait_on_bit_lock
if and only if blocking is allowed. Return -EAGAIN if nonblocking and the
test_and_set of the bit was already locked.
Signed-off-by: Weston Andros Adamson <dros@xxxxxxxxxxxxxxx>
Reviewed-by: Peng Tao <tao.peng@xxxxxxxxxxxxxxx>
Signed-off-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/nfs/pagelist.c | 23 ++++++++++++++---------
1 file changed, 14 insertions(+), 9 deletions(-)
--- a/fs/nfs/pagelist.c
+++ b/fs/nfs/pagelist.c
@@ -149,24 +149,29 @@ static int nfs_wait_bit_uninterruptible(
*
* this lock must be held if modifying the page group list
*
- * returns result from wait_on_bit_lock: 0 on success, < 0 on error
+ * return 0 on success, < 0 on error: -EDELAY if nonblocking or the
+ * result from wait_on_bit_lock
+ *
+ * NOTE: calling with nonblock=false should always have set the
+ * lock bit (see fs/buffer.c and other uses of wait_on_bit_lock
+ * with TASK_UNINTERRUPTIBLE), so there is no need to check the result.
*/
int
nfs_page_group_lock(struct nfs_page *req, bool nonblock)
{
struct nfs_page *head = req->wb_head;
- int ret;
WARN_ON_ONCE(head != head->wb_head);
- do {
- ret = wait_on_bit_lock(&head->wb_flags, PG_HEADLOCK,
- nfs_wait_bit_uninterruptible,
- TASK_UNINTERRUPTIBLE);
- } while (!nonblock && ret != 0);
+ if (!test_and_set_bit(PG_HEADLOCK, &head->wb_flags))
+ return 0;
+
+ if (!nonblock)
+ return wait_on_bit_lock(&head->wb_flags, PG_HEADLOCK,
+ nfs_wait_bit_uninterruptible,
+ TASK_UNINTERRUPTIBLE);
- WARN_ON_ONCE(ret > 0);
- return ret;
+ return -EAGAIN;
}
/*
--
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