Messages in this thread | | | Date | Mon, 5 Feb 2024 13:10:54 +0000 | Subject | Re: [PATCH 4/6] fs: xfs: Support atomic write for statx | From | John Garry <> |
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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@oracle.com> >> --- >> 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
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