On 13/02/2024 17:37, Darrick J. Wong wrote:
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?
The parameter declarations should line up with the local variables:
void
xfs_get_atomic_write_attr(
struct xfs_inode *ip,
unsigned int *unit_min,
unsigned int *unit_max)
{
struct xfs_buftarg *target = xfs_inode_buftarg(ip);
struct block_device *bdev = target->bt_bdev;
struct request_queue *q = bdev->bd_queue;
struct xfs_mount *mp = ip->i_mount;
unsigned int awu_min, awu_max, align;
xfs_extlen_t extsz = xfs_get_extsz(ip);
+{
+ 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_min = roundup(queue_atomic_write_unit_min_bytes(q),
mp->m_sb.sb_blocksize);
?
Yeah, I think that all this can be simplified to be made more obvious.
+ 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
The file allocation unit and hence the return value of
xfs_inode_alloc_unitsize is always a multiple of sb_blocksize.
Right, but this value is coming from HW and we are just ensuring that
the awu_min which we report is >= BLOCKSIZE. xfs_inode_alloc_unitsize()
return value will really guide unit_max.
Anyway, again I can make this all more obvious.
Thanks,
John
