This is a note to let you know that I've just added the patch titled
pNFS: Fix a deadlock when coalescing writes and returning the layout
to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...
The filename of the patch is: pnfs-fix-a-deadlock-when-coalescing-writes-and-returning-the-layout.patch and it can be found in the queue-4.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.
From foo@baz Thu Mar 22 14:40:24 CET 2018
From: Trond Myklebust trond.myklebust@primarydata.com Date: Mon, 1 May 2017 17:06:56 -0400 Subject: pNFS: Fix a deadlock when coalescing writes and returning the layout
From: Trond Myklebust trond.myklebust@primarydata.com
[ Upstream commit 61f454e30c18a28924e96be12592c0d5e24bcc81 ]
Consider the following deadlock:
Process P1 Process P2 Process P3 ========== ========== ========== lock_page(page)
lseg = pnfs_update_layout(inode)
lo = NFS_I(inode)->layout pnfs_error_mark_layout_for_return(lo)
lock_page(page)
lseg = pnfs_update_layout(inode)
In this scenario, - P1 has declared the layout to be in error, but P2 holds a reference to a layout segment on that inode, so the layoutreturn is deferred. - P2 is waiting for a page lock held by P3. - P3 is asking for a new layout segment, but is blocked waiting for the layoutreturn.
The fix is to ensure that pnfs_error_mark_layout_for_return() does not set the NFS_LAYOUT_RETURN flag, which blocks P3. Instead, we allow the latter to call LAYOUTGET so that it can make progress and unblock P2.
Signed-off-by: Trond Myklebust trond.myklebust@primarydata.com Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/nfs/pnfs.c | 2 -- 1 file changed, 2 deletions(-)
--- a/fs/nfs/pnfs.c +++ b/fs/nfs/pnfs.c @@ -1953,8 +1953,6 @@ void pnfs_error_mark_layout_for_return(s
spin_lock(&inode->i_lock); pnfs_set_plh_return_info(lo, range.iomode, 0); - /* Block LAYOUTGET */ - set_bit(NFS_LAYOUT_RETURN, &lo->plh_flags); /* * mark all matching lsegs so that we are sure to have no live * segments at hand when sending layoutreturn. See pnfs_put_lseg()
Patches currently in stable-queue which might be from trond.myklebust@primarydata.com are
queue-4.9/pnfs-fix-use-after-free-issues-in-pnfs_do_read.patch queue-4.9/pnfs-fix-a-deadlock-when-coalescing-writes-and-returning-the-layout.patch queue-4.9/nfs-fix-missing-pg_cleanup-after-nfs_pageio_cond_complete.patch