From bc8a309e88a86205fc3e17f06e42a2e56fc6f807 Mon Sep 17 00:00:00 2001
From: Weston Andros Adamson <dros@primarydata.com>
Date: Fri, 8 Aug 2014 11:00:54 -0400
Subject: nfs: fix nonblocking calls to nfs_page_group_lock
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@primarydata.com>
Reviewed-by: Peng Tao <tao.peng@primarydata.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
---
fs/nfs/pagelist.c | 21 +++++++++++++--------
1 file changed, 13 insertions(+), 8 deletions(-)
(limited to 'fs')
diff --git a/fs/nfs/pagelist.c b/fs/nfs/pagelist.c
index 7efa61586bc4..89d5d433e351 100644
--- a/fs/nfs/pagelist.c
+++ b/fs/nfs/pagelist.c
@@ -143,23 +143,28 @@ nfs_iocounter_wait(struct nfs_io_counter *c)
*
* 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,
- TASK_UNINTERRUPTIBLE);
- } while (!nonblock && ret != 0);
+ if (!test_and_set_bit(PG_HEADLOCK, &head->wb_flags))
+ return 0;
- WARN_ON_ONCE(ret > 0);
- return ret;
+ if (!nonblock)
+ return wait_on_bit_lock(&head->wb_flags, PG_HEADLOCK,
+ TASK_UNINTERRUPTIBLE);
+
+ return -EAGAIN;
}
/*
--
cgit