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xfs: set s_min_writeback_pages for zoned file systems

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Set s_min_writeback_pages to the zone size, so that writeback always
writes up to a full zone.  This ensures that writeback does not add
spurious file fragmentation when writing back a large number of
files that are larger than the zone size.

Fixes: 4e4d520755 ("xfs: add the zoned space allocator")
Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://patch.msgid.link/20251017034611.651385-4-hch@lst.de
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
Christoph Hellwig 2025-10-17 05:45:49 +02:00 committed by Christian Brauner
parent 90db4d4441
commit 015a544077
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GPG Key ID: 91C61BC06578DCA2
1 changed files with 26 additions and 2 deletions
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28
fs/xfs/xfs_zone_alloc.c
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@ -1215,6 +1215,7 @@ xfs_mount_zones(
.mp = mp,
};
struct xfs_buftarg *bt = mp->m_rtdev_targp;
xfs_extlen_t zone_blocks = mp->m_groups[XG_TYPE_RTG].blocks;
int error;
if (!bt) {
@ -1245,10 +1246,33 @@ xfs_mount_zones(
return -ENOMEM;
xfs_info(mp, "%u zones of %u blocks (%u max open zones)",
mp->m_sb.sb_rgcount, mp->m_groups[XG_TYPE_RTG].blocks,
mp->m_max_open_zones);
mp->m_sb.sb_rgcount, zone_blocks, mp->m_max_open_zones);
trace_xfs_zones_mount(mp);
/*
* The writeback code switches between inodes regularly to provide
* fairness. The default lower bound is 4MiB, but for zoned file
* systems we want to increase that both to reduce seeks, but also more
* importantly so that workloads that writes files in a multiple of the
* zone size do not get fragmented and require garbage collection when
* they shouldn't. Increase is to the zone size capped by the max
* extent len.
*
* Note that because s_min_writeback_pages is a superblock field, this
* value also get applied to non-zoned files on the data device if
* there are any. On typical zoned setup all data is on the RT device
* because using the more efficient sequential write required zones
* is the reason for using the zone allocator, and either the RT device
* and the (meta)data device are on the same block device, or the
* (meta)data device is on a fast SSD while the data on the RT device
* is on a SMR HDD. In any combination of the above cases enforcing
* the higher min_writeback_pages for non-RT inodes is either a noop
* or beneficial.
*/
mp->m_super->s_min_writeback_pages =
XFS_FSB_TO_B(mp, min(zone_blocks, XFS_MAX_BMBT_EXTLEN)) >>
PAGE_SHIFT;
if (bdev_is_zoned(bt->bt_bdev)) {
error = blkdev_report_zones(bt->bt_bdev,
XFS_FSB_TO_BB(mp, mp->m_sb.sb_rtstart),