On Wed, Jun 03, 2015 at 06:12:01AM +1000, Dave Chinner wrote:
> On Tue, Jun 02, 2015 at 12:02:59PM -0400, Brian Foster wrote:
> > On Fri, May 29, 2015 at 09:45:52AM +1000, Dave Chinner wrote:
> > > From: Dave Chinner <dchinner@xxxxxxxxxx>
> > >
> > > Add initial support for DAX block zeroing operations to XFS. DAX
> > > cannot use buffered IO through the page cache for zeroing, nor do we
> > > need to issue IO for uncached block zeroing. In both cases, we can
> > > simply call out to the dax block zeroing function.
> > >
> > > Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>
> > > ---
> > > fs/xfs/xfs_bmap_util.c | 23 +++++++++++++++++++----
> > > fs/xfs/xfs_file.c | 43 +++++++++++++++++++++++++------------------
> > > 2 files changed, 44 insertions(+), 22 deletions(-)
> > >
> > ...
> > > @@ -108,20 +110,25 @@ xfs_iozero(
> > > if (bytes > count)
> > > bytes = count;
> > >
> > > - status = pagecache_write_begin(NULL, mapping, pos, bytes,
> > > - AOP_FLAG_UNINTERRUPTIBLE,
> > > - &page, &fsdata);
> > > - if (status)
> > > - break;
> > > + if (IS_DAX(VFS_I(ip)))
> > > + dax_zero_page_range(VFS_I(ip), pos, bytes,
> > > + xfs_get_blocks_direct);
> >
> > Still no error checking here...
>
> Ah. missed that. Updated patch below.
>
> Cheers,
>
> Dave.
> --
> Dave Chinner
> david@xxxxxxxxxxxxx
>
> xfs: add DAX block zeroing support
>
> From: Dave Chinner <dchinner@xxxxxxxxxx>
>
> Add initial support for DAX block zeroing operations to XFS. DAX
> cannot use buffered IO through the page cache for zeroing, nor do we
> need to issue IO for uncached block zeroing. In both cases, we can
> simply call out to the dax block zeroing function.
>
> Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>
> ---
Thanks!
Reviewed-by: Brian Foster <bfoster@xxxxxxxxxx>
> fs/xfs/xfs_bmap_util.c | 23 +++++++++++++++++++----
> fs/xfs/xfs_file.c | 45 +++++++++++++++++++++++++++------------------
> 2 files changed, 46 insertions(+), 22 deletions(-)
>
> diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c
> index a52bbd3..4a29655 100644
> --- a/fs/xfs/xfs_bmap_util.c
> +++ b/fs/xfs/xfs_bmap_util.c
> @@ -1133,14 +1133,29 @@ xfs_zero_remaining_bytes(
> break;
> ASSERT(imap.br_blockcount >= 1);
> ASSERT(imap.br_startoff == offset_fsb);
> + ASSERT(imap.br_startblock != DELAYSTARTBLOCK);
> +
> + if (imap.br_startblock == HOLESTARTBLOCK ||
> + imap.br_state == XFS_EXT_UNWRITTEN) {
> + /* skip the entire extent */
> + lastoffset = XFS_FSB_TO_B(mp, imap.br_startoff +
> + imap.br_blockcount) - 1;
> + continue;
> + }
> +
> lastoffset = XFS_FSB_TO_B(mp, imap.br_startoff + 1) - 1;
> if (lastoffset > endoff)
> lastoffset = endoff;
> - if (imap.br_startblock == HOLESTARTBLOCK)
> - continue;
> - ASSERT(imap.br_startblock != DELAYSTARTBLOCK);
> - if (imap.br_state == XFS_EXT_UNWRITTEN)
> +
> + /* DAX can just zero the backing device directly */
> + if (IS_DAX(VFS_I(ip))) {
> + error = dax_zero_page_range(VFS_I(ip), offset,
> + lastoffset - offset + 1,
> + xfs_get_blocks_direct);
> + if (error)
> + return error;
> continue;
> + }
>
> error = xfs_buf_read_uncached(XFS_IS_REALTIME_INODE(ip) ?
> mp->m_rtdev_targp : mp->m_ddev_targp,
> diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
> index c2af282..84b2421 100644
> --- a/fs/xfs/xfs_file.c
> +++ b/fs/xfs/xfs_file.c
> @@ -79,14 +79,15 @@ xfs_rw_ilock_demote(
> }
>
> /*
> - * xfs_iozero
> + * xfs_iozero clears the specified range supplied via the page cache (except in
> + * the DAX case). Writes through the page cache will allocate blocks over holes,
> + * though the callers usually map the holes first and avoid them. If a block is
> + * not completely zeroed, then it will be read from disk before being partially
> + * zeroed.
> *
> - * xfs_iozero clears the specified range of buffer supplied,
> - * and marks all the affected blocks as valid and modified. If
> - * an affected block is not allocated, it will be allocated. If
> - * an affected block is not completely overwritten, and is not
> - * valid before the operation, it will be read from disk before
> - * being partially zeroed.
> + * In the DAX case, we can just directly write to the underlying pages. This
> + * will not allocate blocks, but will avoid holes and unwritten extents and so
> + * not do unnecessary work.
> */
> int
> xfs_iozero(
> @@ -96,7 +97,8 @@ xfs_iozero(
> {
> struct page *page;
> struct address_space *mapping;
> - int status;
> + int status = 0;
> +
>
> mapping = VFS_I(ip)->i_mapping;
> do {
> @@ -108,20 +110,27 @@ xfs_iozero(
> if (bytes > count)
> bytes = count;
>
> - status = pagecache_write_begin(NULL, mapping, pos, bytes,
> - AOP_FLAG_UNINTERRUPTIBLE,
> - &page, &fsdata);
> - if (status)
> - break;
> + if (IS_DAX(VFS_I(ip))) {
> + status = dax_zero_page_range(VFS_I(ip), pos, bytes,
> + xfs_get_blocks_direct);
> + if (status)
> + break;
> + } else {
> + status = pagecache_write_begin(NULL, mapping, pos, bytes,
> + AOP_FLAG_UNINTERRUPTIBLE,
> + &page, &fsdata);
> + if (status)
> + break;
>
> - zero_user(page, offset, bytes);
> + zero_user(page, offset, bytes);
>
> - status = pagecache_write_end(NULL, mapping, pos, bytes, bytes,
> - page, fsdata);
> - WARN_ON(status <= 0); /* can't return less than zero! */
> + status = pagecache_write_end(NULL, mapping, pos, bytes,
> + bytes, page, fsdata);
> + WARN_ON(status <= 0); /* can't return less than zero! */
> + status = 0;
> + }
> pos += bytes;
> count -= bytes;
> - status = 0;
> } while (count);
>
> return status;
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