From 6bb2270223a8128efdcaf1654ba416f693eb4623 Mon Sep 17 00:00:00 2001 From: NeilBrown Date: Mon, 7 Mar 2022 10:41:44 +1100 Subject: NFS: swap-out must always use STABLE writes. [ 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 Signed-off-by: Trond Myklebust Signed-off-by: Sasha Levin --- fs/nfs/direct.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) (limited to 'fs') diff --git a/fs/nfs/direct.c b/fs/nfs/direct.c index 28afc315ec0c..c220810c61d1 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, -- cgit v1.2.3