On Tue, Apr 26, 2022 at 10:43:23AM -0700, Stefan Roesch wrote:
> This adds the async buffered write support to the iomap layer of XFS. If
> a lock cannot be acquired or additional reads need to be performed, the
> request will return -EAGAIN in case this is an async buffered write request.
>
> Signed-off-by: Stefan Roesch <shr@xxxxxx>
> ---
> fs/xfs/xfs_iomap.c | 33 +++++++++++++++++++++++++++++++--
> 1 file changed, 31 insertions(+), 2 deletions(-)
>
> diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
> index e552ce541ec2..80b6c48e88af 100644
> --- a/fs/xfs/xfs_iomap.c
> +++ b/fs/xfs/xfs_iomap.c
> @@ -881,18 +881,28 @@ xfs_buffered_write_iomap_begin(
> bool eof = false, cow_eof = false, shared = false;
> int allocfork = XFS_DATA_FORK;
> int error = 0;
> + bool no_wait = (flags & IOMAP_NOWAIT);
>
> if (xfs_is_shutdown(mp))
> return -EIO;
>
> /* we can't use delayed allocations when using extent size hints */
> - if (xfs_get_extsz_hint(ip))
> + if (xfs_get_extsz_hint(ip)) {
> + if (no_wait)
> + return -EAGAIN;
> +
> return xfs_direct_write_iomap_begin(inode, offset, count,
> flags, iomap, srcmap);
Why can't we do IOMAP_NOWAIT allocation here?
xfs_direct_write_iomap_begin() supports IOMAP_NOWAIT semantics just
fine - that's what the direct IO path uses...
> + }
>
> ASSERT(!XFS_IS_REALTIME_INODE(ip));
>
> - xfs_ilock(ip, XFS_ILOCK_EXCL);
> + if (no_wait) {
> + if (!xfs_ilock_nowait(ip, XFS_ILOCK_EXCL))
> + return -EAGAIN;
> + } else {
> + xfs_ilock(ip, XFS_ILOCK_EXCL);
> + }
handled by xfs_ilock_for_iomap().
>
> if (XFS_IS_CORRUPT(mp, !xfs_ifork_has_extents(&ip->i_df)) ||
> XFS_TEST_ERROR(false, mp, XFS_ERRTAG_BMAPIFORMAT)) {
> @@ -902,6 +912,11 @@ xfs_buffered_write_iomap_begin(
>
> XFS_STATS_INC(mp, xs_blk_mapw);
>
> + if (no_wait && xfs_need_iread_extents(XFS_IFORK_PTR(ip, XFS_DATA_FORK))) {
> + error = -EAGAIN;
> + goto out_unlock;
> + }
> +
Also handled by xfs_ilock_for_iomap().
> error = xfs_iread_extents(NULL, ip, XFS_DATA_FORK);
> if (error)
> goto out_unlock;
> @@ -933,6 +948,10 @@ xfs_buffered_write_iomap_begin(
> if (xfs_is_cow_inode(ip)) {
> if (!ip->i_cowfp) {
> ASSERT(!xfs_is_reflink_inode(ip));
> + if (no_wait) {
> + error = -EAGAIN;
> + goto out_unlock;
> + }
> xfs_ifork_init_cow(ip);
> }
Also handled by xfs_ilock_for_iomap().
> cow_eof = !xfs_iext_lookup_extent(ip, ip->i_cowfp, offset_fsb,
> @@ -956,6 +975,11 @@ xfs_buffered_write_iomap_begin(
> goto found_imap;
> }
>
> + if (no_wait) {
> + error = -EAGAIN;
> + goto out_unlock;
> + }
> +
Won't get here because this is COW path, and xfs_ilock_for_iomap()
handles returning -EAGAIN for that case.
> xfs_trim_extent(&imap, offset_fsb, end_fsb - offset_fsb);
>
> /* Trim the mapping to the nearest shared extent boundary. */
> @@ -993,6 +1017,11 @@ xfs_buffered_write_iomap_begin(
> allocfork = XFS_COW_FORK;
> }
>
> + if (no_wait) {
> + error = -EAGAIN;
> + goto out_unlock;
> + }
Why? Delayed allocation doesn't block...
Cheers,
Dave.
--
Dave Chinner
david@xxxxxxxxxxxxx
