On Wed, May 24, 2017 at 11:41:49AM -0500, Goldwyn Rodrigues wrote:
> From: Goldwyn Rodrigues <rgold...@suse.com>
>
> If IOCB_NOWAIT is set, bail if the i_rwsem is not lockable
> immediately.
>
> IF IOMAP_NOWAIT is set, return EAGAIN in xfs_file_iomap_begin
> if it needs allocation either due to file extension, writing to a hole,
> or COW or waiting for other DIOs to finish.
>
> Signed-off-by: Goldwyn Rodrigues <rgold...@suse.com>
> Reviewed-by: Christoph Hellwig <h...@lst.de>
Looks good,
Reviewed-by: Darrick J. Wong <darrick.w...@oracle.com>
--D
> ---
> fs/xfs/xfs_file.c | 19 ++++++++++++++-----
> fs/xfs/xfs_iomap.c | 17 +++++++++++++++++
> 2 files changed, 31 insertions(+), 5 deletions(-)
>
> diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
> index 35703a801372..b307940e7d56 100644
> --- a/fs/xfs/xfs_file.c
> +++ b/fs/xfs/xfs_file.c
> @@ -541,8 +541,11 @@ xfs_file_dio_aio_write(
> iolock = XFS_IOLOCK_SHARED;
> }
>
> - xfs_ilock(ip, iolock);
> -
> + if (!xfs_ilock_nowait(ip, iolock)) {
> + if (iocb->ki_flags & IOCB_NOWAIT)
> + return -EAGAIN;
> + xfs_ilock(ip, iolock);
> + }
> ret = xfs_file_aio_write_checks(iocb, from, &iolock);
> if (ret)
> goto out;
> @@ -553,9 +556,15 @@ xfs_file_dio_aio_write(
> * otherwise demote the lock if we had to take the exclusive lock
> * for other reasons in xfs_file_aio_write_checks.
> */
> - if (unaligned_io)
> - inode_dio_wait(inode);
> - else if (iolock == XFS_IOLOCK_EXCL) {
> + if (unaligned_io) {
> + /* If we are going to wait for other DIO to finish, bail */
> + if (iocb->ki_flags & IOCB_NOWAIT) {
> + if (atomic_read(&inode->i_dio_count))
> + return -EAGAIN;
> + } else {
> + inode_dio_wait(inode);
> + }
> + } else if (iolock == XFS_IOLOCK_EXCL) {
> xfs_ilock_demote(ip, XFS_IOLOCK_EXCL);
> iolock = XFS_IOLOCK_SHARED;
> }
> diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
> index 94e5bdf7304c..8b0e3c1e086d 100644
> --- a/fs/xfs/xfs_iomap.c
> +++ b/fs/xfs/xfs_iomap.c
> @@ -1016,6 +1016,15 @@ xfs_file_iomap_begin(
>
> if ((flags & (IOMAP_WRITE | IOMAP_ZERO)) && xfs_is_reflink_inode(ip)) {
> if (flags & IOMAP_DIRECT) {
> + /*
> + * A reflinked inode will result in CoW alloc.
> + * FIXME: It could still overwrite on unshared extents
> + * and not need allocation.
> + */
> + if (flags & IOMAP_NOWAIT) {
> + error = -EAGAIN;
> + goto out_unlock;
> + }
> /* may drop and re-acquire the ilock */
> error = xfs_reflink_allocate_cow(ip, &imap, &shared,
> &lockmode);
> @@ -1033,6 +1042,14 @@ xfs_file_iomap_begin(
>
> if ((flags & IOMAP_WRITE) && imap_needs_alloc(inode, &imap, nimaps)) {
> /*
> + * If nowait is set bail since we are going to make
> + * allocations.
> + */
> + if (flags & IOMAP_NOWAIT) {
> + error = -EAGAIN;
> + goto out_unlock;
> + }
> + /*
> * We cap the maximum length we map here to MAX_WRITEBACK_PAGES
> * pages to keep the chunks of work done where somewhat
> symmetric
> * with the work writeback does. This is a completely arbitrary
> --
> 2.12.0
>
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