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    Subject[PATCH 18/18] NFS: swap-out must always use STABLE writes.
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    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_COND_STABLE.

    Signed-off-by: NeilBrown <neilb@suse.de>
    ---
    fs/nfs/direct.c | 7 ++++---
    1 file changed, 4 insertions(+), 3 deletions(-)

    diff --git a/fs/nfs/direct.c b/fs/nfs/direct.c
    index eeff1b4e1a7c..1317465150a6 100644
    --- a/fs/nfs/direct.c
    +++ b/fs/nfs/direct.c
    @@ -790,7 +790,7 @@ 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;
    @@ -798,7 +798,7 @@ 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);
    @@ -904,6 +904,7 @@ ssize_t nfs_file_direct_write(struct kiocb *iocb, struct iov_iter *iter,
    struct nfs_direct_req *dreq;
    struct nfs_lock_context *l_ctx;
    loff_t pos, end;
    + int ioflags = swap ? FLUSH_COND_STABLE : FLUSH_STABLE;

    dfprintk(FILE, "NFS: direct write(%pD2, %zd@%Ld)\n",
    file, iov_iter_count(iter), (long long) iocb->ki_pos);
    @@ -946,7 +947,7 @@ ssize_t nfs_file_direct_write(struct kiocb *iocb, struct iov_iter *iter,
    if (!swap)
    nfs_start_io_direct(inode);

    - requested = nfs_direct_write_schedule_iovec(dreq, iter, pos);
    + requested = nfs_direct_write_schedule_iovec(dreq, iter, pos, ioflags);

    if (mapping->nrpages) {
    invalidate_inode_pages2_range(mapping,

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