diff options
author | Trond Myklebust <trond.myklebust@primarydata.com> | 2017-05-01 17:06:56 -0400 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2018-03-24 11:00:21 +0100 |
commit | 1b9c9549b2c9814d35b22fa817466226d9fbb8e5 (patch) | |
tree | 05378e180b27949a8939eb89adf5423ee66718b0 /fs | |
parent | e22a6754abda4ab563fce3f3241e71a8c917c979 (diff) |
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 <trond.myklebust@primarydata.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'fs')
-rw-r--r-- | fs/nfs/pnfs.c | 2 |
1 files changed, 0 insertions, 2 deletions
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() |