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| author |   NeilBrown <neilb@suse.de> | 2022-03-07 10:41:44 +1100 |
|---|---|---|
| committer |   Trond Myklebust <trond.myklebust@hammerspace.com> | 2022-03-13 12:59:35 -0400 |
| commit | c265de257f558a05c1859ee9e3fed04883b9ec0e (patch) | |
| tree | 3f1f684db4b2c37bbdcdf9f82a232fe33cacfc85 /fs/nfs/direct.c | |
| parent | NFS: swap IO handling is slightly different for O_DIRECT IO (diff) | |
| download | linux-dev-c265de257f558a05c1859ee9e3fed04883b9ec0e.tar.xz linux-dev-c265de257f558a05c1859ee9e3fed04883b9ec0e.zip | |
NFS: swap-out must always use STABLE writes.
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>
Diffstat (limited to 'fs/nfs/direct.c')
| -rw-r--r-- | fs/nfs/direct.c | 10 |
1 files changed, 6 insertions, 4 deletions
diff --git a/fs/nfs/direct.c b/fs/nfs/direct.c index 04aaf39a05cb..11c566d8769f 100644 --- a/fs/nfs/direct.c +++ b/fs/nfs/direct.c @@ -794,7 +794,7 @@ 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; @@ -802,7 +802,7 @@ 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); @@ -948,11 +948,13 @@ 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, |