From: Trond Myklebust Date: Mon, 1 May 2017 21:06:56 +0000 (-0400) Subject: pNFS: Fix a deadlock when coalescing writes and returning the layout X-Git-Tag: android-x86-7.1-r2~1^2~34^2~54 X-Git-Url: http://git.osdn.net/view?a=commitdiff_plain;h=1b9c9549b2c9814d35b22fa817466226d9fbb8e5;p=android-x86%2Fkernel.git pNFS: Fix a deadlock when coalescing writes and returning the layout [ 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 Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c index e9a697e9d292..0e008db16b16 100644 --- a/fs/nfs/pnfs.c +++ b/fs/nfs/pnfs.c @@ -1953,8 +1953,6 @@ void pnfs_error_mark_layout_for_return(struct inode *inode, 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()