From: Weston Andros Adamson Date: Mon, 15 Sep 2014 18:14:40 +0000 (-0400) Subject: nfs: fix nonblocking calls to nfs_page_group_lock X-Git-Tag: v3.16.4~191 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=28c86fda6b1d637bac19a72c5db5cce90b043b95;p=thirdparty%2Fkernel%2Fstable.git nfs: fix nonblocking calls to nfs_page_group_lock 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 Reviewed-by: Peng Tao Signed-off-by: Trond Myklebust Signed-off-by: Greg Kroah-Hartman --- diff --git a/fs/nfs/pagelist.c b/fs/nfs/pagelist.c index b4ebd4d7d9765..c27a05c27c116 100644 --- a/fs/nfs/pagelist.c +++ b/fs/nfs/pagelist.c @@ -149,24 +149,29 @@ static int nfs_wait_bit_uninterruptible(void *word) * * 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; - WARN_ON_ONCE(ret > 0); - return ret; + if (!nonblock) + return wait_on_bit_lock(&head->wb_flags, PG_HEADLOCK, + nfs_wait_bit_uninterruptible, + TASK_UNINTERRUPTIBLE); + + return -EAGAIN; } /*