| From | Greg Kroah-Hartman <> | Subject | [PATCH 3.16 168/357] nfs: fix nonblocking calls to nfs_page_group_lock | Date | Fri, 3 Oct 2014 14:29:14 -0700 |
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3.16-stable review patch. If anyone has any objections, please let me know.
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From: Weston Andros Adamson <dros@primarydata.com>
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@primarydata.com> Reviewed-by: Peng Tao <tao.peng@primarydata.com> Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> --- 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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