[PATCH v2 08/14] fs: xfs: iomap: Sub-extent zeroing

John Garry
2024-03-04T13:05:31Z

Set iomap->extent_shift when sub-extent zeroing is required.

We treat a sub-extent write same as an unaligned write, so we can leverage
the existing sub-FSblock unaligned write support, i.e. try a shared lock
with IOMAP_DIO_OVERWRITE_ONLY flag, if this fails then try the exclusive
lock.

In xfs_iomap_write_unwritten(), FSB calcs are now based on the extsize.

Signed-off-by: John Garry <john.g.garry@oracle.com>
---
fs/xfs/xfs_file.c | 28 +++++++++++++++-------------
fs/xfs/xfs_iomap.c | 15 +++++++++++++--
2 files changed, 28 insertions(+), 15 deletions(-)

diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index e33e5e13b95f..d0bd9d5f596c 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -617,18 +617,19 @@ xfs_file_dio_write_aligned(
* Handle block unaligned direct I/O writes
*
* In most cases direct I/O writes will be done holding IOLOCK_SHARED, allowing
- * them to be done in parallel with reads and other direct I/O writes. However,
- * if the I/O is not aligned to filesystem blocks, the direct I/O layer may need
- * to do sub-block zeroing and that requires serialisation against other direct
- * I/O to the same block. In this case we need to serialise the submission of
- * the unaligned I/O so that we don't get racing block zeroing in the dio layer.
- * In the case where sub-block zeroing is not required, we can do concurrent
- * sub-block dios to the same block successfully.
+ * them to be done in parallel with reads and other direct I/O writes.
+ * However if the I/O is not aligned to filesystem blocks/extent, the direct
+ * I/O layer may need to do sub-block/extent zeroing and that requires
+ * serialisation against other direct I/O to the same block/extent. In this
+ * case we need to serialise the submission of the unaligned I/O so that we
+ * don't get racing block/extent zeroing in the dio layer.
+ * In the case where sub-block/extent zeroing is not required, we can do
+ * concurrent sub-block/extent dios to the same block/extent successfully.
*
* Optimistically submit the I/O using the shared lock first, but use the
* IOMAP_DIO_OVERWRITE_ONLY flag to tell the lower layers to return -EAGAIN
- * if block allocation or partial block zeroing would be required. In that case
- * we try again with the exclusive lock.
+ * if block/extent allocation or partial block/extent zeroing would be
+ * required. In that case we try again with the exclusive lock.
*/
static noinline ssize_t
xfs_file_dio_write_unaligned(
@@ -643,9 +644,9 @@ xfs_file_dio_write_unaligned(
ssize_t ret;

/*
- * Extending writes need exclusivity because of the sub-block zeroing
- * that the DIO code always does for partial tail blocks beyond EOF, so
- * don't even bother trying the fast path in this case.
+ * Extending writes need exclusivity because of the sub-block/extent
+ * zeroing that the DIO code always does for partial tail blocks
+ * beyond EOF, so don't even bother trying the fast path in this case.
*/
if (iocb->ki_pos > isize || iocb->ki_pos + count >= isize) {
if (iocb->ki_flags & IOCB_NOWAIT)
@@ -709,13 +710,14 @@ xfs_file_dio_write(
struct iov_iter *from)
{
struct xfs_inode *ip = XFS_I(file_inode(iocb->ki_filp));
+ struct xfs_mount *mp = ip->i_mount;
struct xfs_buftarg *target = xfs_inode_buftarg(ip);
size_t count = iov_iter_count(from);

/* direct I/O must be aligned to device logical sector size */
if ((iocb->ki_pos | count) & target->bt_logical_sectormask)
return -EINVAL;
- if ((iocb->ki_pos | count) & ip->i_mount->m_blockmask)
+ if ((iocb->ki_pos | count) & (XFS_FSB_TO_B(mp, xfs_get_extsz(ip)) - 1))
return xfs_file_dio_write_unaligned(ip, iocb, from);
return xfs_file_dio_write_aligned(ip, iocb, from);
}
diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
index 70fe873951f3..88cc20bb19c9 100644
--- a/fs/xfs/xfs_iomap.c
+++ b/fs/xfs/xfs_iomap.c
@@ -98,6 +98,7 @@ xfs_bmbt_to_iomap(
{
struct xfs_mount *mp = ip->i_mount;
struct xfs_buftarg *target = xfs_inode_buftarg(ip);
+ xfs_extlen_t extsz = xfs_get_extsz(ip);

if (unlikely(!xfs_valid_startblock(ip, imap->br_startblock)))
return xfs_alert_fsblock_zero(ip, imap);
@@ -134,6 +135,8 @@ xfs_bmbt_to_iomap(

iomap->validity_cookie = sequence_cookie;
iomap->folio_ops = &xfs_iomap_folio_ops;
+ if (extsz > 1)
+ iomap->extent_shift = ffs(extsz) - 1;
return 0;
}

@@ -563,11 +566,19 @@ xfs_iomap_write_unwritten(
xfs_fsize_t i_size;
uint resblks;
int error;
+ xfs_extlen_t extsz = xfs_get_extsz(ip);

trace_xfs_unwritten_convert(ip, offset, count);

- offset_fsb = XFS_B_TO_FSBT(mp, offset);
- count_fsb = XFS_B_TO_FSB(mp, (xfs_ufsize_t)offset + count);
+ if (extsz > 1) {
+ xfs_extlen_t extsize_bytes = XFS_FSB_TO_B(mp, extsz);
+
+ offset_fsb = XFS_B_TO_FSBT(mp, round_down(offset, extsize_bytes));
+ count_fsb = XFS_B_TO_FSB(mp, round_up(offset + count, extsize_bytes));
+ } else {
+ offset_fsb = XFS_B_TO_FSBT(mp, offset);
+ count_fsb = XFS_B_TO_FSB(mp, (xfs_ufsize_t)offset + count);
+ }
count_fsb = (xfs_filblks_t)(count_fsb - offset_fsb);

/*
--
2.31.1