On 02/02/2024 18:05, Darrick J. Wong wrote:
On Wed, Jan 24, 2024 at 02:26:43PM +0000, John Garry wrote:
Support providing info on atomic write unit min and max for an inode.
For simplicity, currently we limit the min at the FS block size, but a
lower limit could be supported in future.
The atomic write unit min and max is limited by the guaranteed extent
alignment for the inode.
Signed-off-by: John Garry <john.g.garry@xxxxxxxxxx>
---
fs/xfs/xfs_iops.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
fs/xfs/xfs_iops.h | 4 ++++
2 files changed, 49 insertions(+)
diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
index a0d77f5f512e..0890d2f70f4d 100644
--- a/fs/xfs/xfs_iops.c
+++ b/fs/xfs/xfs_iops.c
@@ -546,6 +546,44 @@ xfs_stat_blksize(
return PAGE_SIZE;
}
+void xfs_get_atomic_write_attr(
static void?
We use this in the iomap and statx code
+ struct xfs_inode *ip,
+ unsigned int *unit_min,
+ unsigned int *unit_max)
Weird indenting here.
hmmm... I thought that this was the XFS style
Can you show how it should look?
+{
+ xfs_extlen_t extsz = xfs_get_extsz(ip);
+ struct xfs_buftarg *target = xfs_inode_buftarg(ip);
+ struct block_device *bdev = target->bt_bdev;
+ unsigned int awu_min, awu_max, align;
+ struct request_queue *q = bdev->bd_queue;
+ struct xfs_mount *mp = ip->i_mount;
+
+ /*
+ * Convert to multiples of the BLOCKSIZE (as we support a minimum
+ * atomic write unit of BLOCKSIZE).
+ */
+ awu_min = queue_atomic_write_unit_min_bytes(q);
+ awu_max = queue_atomic_write_unit_max_bytes(q);
+
+ awu_min &= ~mp->m_blockmask;
Why do you round /down/ the awu_min value here?
This is just to ensure that we returning *unit_min >= BLOCKSIZE
For example, if awu_min, max 1K, 64K from the bdev, we now have 0 and
64K. And below this gives us awu_min, max of 4k, 64k.
Maybe there is a more logical way of doing this.
+ awu_max &= ~mp->m_blockmask;
Actually -- since the atomic write units have to be powers of 2, why is
rounding needed here at all?
Sure, but the bdev can report a awu_min < BLOCKSIZE
+
+ align = XFS_FSB_TO_B(mp, extsz);
+
+ if (!awu_max || !xfs_inode_atomicwrites(ip) || !align ||
+ !is_power_of_2(align)) {
...and if you take my suggestion to make a common helper to validate the
atomic write unit parameters, this can collapse into:
alloc_unit_bytes = xfs_inode_alloc_unitsize(ip);
if (!xfs_inode_has_atomicwrites(ip) ||
!bdev_validate_atomic_write(bdev, alloc_unit_bytes)) > /* not supported, return zeroes */
*unit_min = 0;
*unit_max = 0;
return;
}
*unit_min = max(alloc_unit_bytes, awu_min);
*unit_max = min(alloc_unit_bytes, awu_max);
Again, we need to ensure that *unit_min >= BLOCKSIZE
Thanks,
John
