| From 45cacb4175715c3b62f6efa093de98b2ca84d67b Mon Sep 17 00:00:00 2001 |
| From: Sasha Levin <sashal@kernel.org> |
| Date: Mon, 7 Mar 2022 10:41:44 +1100 |
| Subject: NFS: swap-out must always use STABLE writes. |
| |
| From: NeilBrown <neilb@suse.de> |
| |
| [ Upstream commit c265de257f558a05c1859ee9e3fed04883b9ec0e ] |
| |
| The commit handling code is not safe against memory-pressure deadlocks |
| when writing to swap. In particular, nfs_commitdata_alloc() blocks |
| indefinitely waiting for memory, and this can consume all available |
| workqueue threads. |
| |
| swap-out most likely uses STABLE writes anyway as COND_STABLE indicates |
| that a stable write should be used if the write fits in a single |
| request, and it normally does. However if we ever swap with a small |
| wsize, or gather unusually large numbers of pages for a single write, |
| this might change. |
| |
| For safety, make it explicit in the code that direct writes used for swap |
| must always use FLUSH_STABLE. |
| |
| Signed-off-by: NeilBrown <neilb@suse.de> |
| Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com> |
| Signed-off-by: Sasha Levin <sashal@kernel.org> |
| --- |
| fs/nfs/direct.c | 10 ++++++---- |
| 1 file changed, 6 insertions(+), 4 deletions(-) |
| |
| diff --git a/fs/nfs/direct.c b/fs/nfs/direct.c |
| index e6f104b6f065..737b30792ac4 100644 |
| --- a/fs/nfs/direct.c |
| +++ b/fs/nfs/direct.c |
| @@ -793,7 +793,7 @@ static const struct nfs_pgio_completion_ops nfs_direct_write_completion_ops = { |
| */ |
| static ssize_t nfs_direct_write_schedule_iovec(struct nfs_direct_req *dreq, |
| struct iov_iter *iter, |
| - loff_t pos) |
| + loff_t pos, int ioflags) |
| { |
| struct nfs_pageio_descriptor desc; |
| struct inode *inode = dreq->inode; |
| @@ -801,7 +801,7 @@ static ssize_t nfs_direct_write_schedule_iovec(struct nfs_direct_req *dreq, |
| size_t requested_bytes = 0; |
| size_t wsize = max_t(size_t, NFS_SERVER(inode)->wsize, PAGE_SIZE); |
| |
| - nfs_pageio_init_write(&desc, inode, FLUSH_COND_STABLE, false, |
| + nfs_pageio_init_write(&desc, inode, ioflags, false, |
| &nfs_direct_write_completion_ops); |
| desc.pg_dreq = dreq; |
| get_dreq(dreq); |
| @@ -947,11 +947,13 @@ ssize_t nfs_file_direct_write(struct kiocb *iocb, struct iov_iter *iter, |
| pnfs_init_ds_commit_info_ops(&dreq->ds_cinfo, inode); |
| |
| if (swap) { |
| - requested = nfs_direct_write_schedule_iovec(dreq, iter, pos); |
| + requested = nfs_direct_write_schedule_iovec(dreq, iter, pos, |
| + FLUSH_STABLE); |
| } else { |
| nfs_start_io_direct(inode); |
| |
| - requested = nfs_direct_write_schedule_iovec(dreq, iter, pos); |
| + requested = nfs_direct_write_schedule_iovec(dreq, iter, pos, |
| + FLUSH_COND_STABLE); |
| |
| if (mapping->nrpages) { |
| invalidate_inode_pages2_range(mapping, |
| -- |
| 2.35.1 |
| |