summaryrefslogtreecommitdiff
path: root/fs/nfs/write.c
diff options
context:
space:
mode:
authorNeilBrown <neilb@suse.de>2014-09-24 05:28:32 +0400
committerTrond Myklebust <trond.myklebust@primarydata.com>2014-09-25 16:25:28 +0400
commit9590544694becc64f4874963dbfc4b4d391024b7 (patch)
treee0578565ba34391968b509cc5cc8cc1ae7d89614 /fs/nfs/write.c
parenta4796e37c12e177572b80864cbab9c907ea250b0 (diff)
downloadlinux-9590544694becc64f4874963dbfc4b4d391024b7.tar.xz
NFS: avoid deadlocks with loop-back mounted NFS filesystems.
Support for loop-back mounted NFS filesystems is useful when NFS is used to access shared storage in a high-availability cluster. If the node running the NFS server fails, some other node can mount the filesystem and start providing NFS service. If that node already had the filesystem NFS mounted, it will now have it loop-back mounted. nfsd can suffer a deadlock when allocating memory and entering direct reclaim. While direct reclaim does not write to the NFS filesystem it can send and wait for a COMMIT through nfs_release_page(). This patch modifies nfs_release_page() to wait a limited time for the commit to complete - one second. If the commit doesn't complete in this time, nfs_release_page() will fail. This means it might now fail in some cases where it wouldn't before. These cases are only when 'gfp' includes '__GFP_WAIT'. nfs_release_page() is only called by try_to_release_page(), and that can only be called on an NFS page with required 'gfp' flags from - page_cache_pipe_buf_steal() in splice.c - shrink_page_list() in vmscan.c - invalidate_inode_pages2_range() in truncate.c The first two handle failure quite safely. The last is only called after ->launder_page() has been called, and that will have waited for the commit to finish already. So aborting if the commit takes longer than 1 second is perfectly safe. Signed-off-by: NeilBrown <neilb@suse.de> Acked-by: Jeff Layton <jlayton@primarydata.com> Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Diffstat (limited to 'fs/nfs/write.c')
-rw-r--r--fs/nfs/write.c2
1 files changed, 2 insertions, 0 deletions
diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index a623b00530c3..c063a4e70354 100644
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -705,6 +705,8 @@ static void nfs_inode_remove_request(struct nfs_page *req)
if (likely(!PageSwapCache(head->wb_page))) {
set_page_private(head->wb_page, 0);
ClearPagePrivate(head->wb_page);
+ smp_mb__after_atomic();
+ wake_up_page(head->wb_page, PG_private);
clear_bit(PG_MAPPED, &head->wb_flags);
}
nfsi->npages--;