[PATCH 2/6] xfs: add DAX block zeroing support

Dave Chinner
2015-03-03T23:31:20Z

From: Dave Chinner <dchinner@redhat.com>

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@redhat.com>
---
fs/xfs/xfs_bmap_util.c | 23 +++++++++++++++++++----
fs/xfs/xfs_file.c | 28 +++++++++++++++++-----------
2 files changed, 36 insertions(+), 15 deletions(-)

diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c
index 1bd5393..d1fe432 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_dax);
+ 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 dc5f609..bc0008f 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -97,7 +97,8 @@ xfs_iozero(
{
struct page *page;
struct address_space *mapping;
- int status;
+ int status = 0;
+

mapping = VFS_I(ip)->i_mapping;
do {
@@ -109,20 +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_dax);
+ 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);
--
2.0.0