[PATCH 5.15 011/136] btrfs: zoned: revive max_zone_append_bytes

Greg Kroah-Hartman
2022-08-29T11:04:42Z

From: Naohiro Aota <naohiro.aota@wdc.com>

commit c2ae7b772ef4e86c5ddf3fd47bf59045ae96a414 upstream

This patch is basically a revert of commit 5a80d1c6a270 ("btrfs: zoned:
remove max_zone_append_size logic"), but without unnecessary ASSERT and
check. The max_zone_append_size will be used as a hint to estimate the
number of extents to cover delalloc/writeback region in the later commits.

The size of a ZONE APPEND bio is also limited by queue_max_segments(), so
this commit considers it to calculate max_zone_append_size. Technically, a
bio can be larger than queue_max_segments() * PAGE_SIZE if the pages are
contiguous. But, it is safe to consider "queue_max_segments() * PAGE_SIZE"
as an upper limit of an extent size to calculate the number of extents
needed to write data.

Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/btrfs/ctree.h | 2 ++
fs/btrfs/zoned.c | 17 +++++++++++++++++
fs/btrfs/zoned.h | 1 +
3 files changed, 20 insertions(+)

--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1017,6 +1017,8 @@ struct btrfs_fs_info {
u64 zoned;
};

+ /* Max size to emit ZONE_APPEND write command */
+ u64 max_zone_append_size;
struct mutex zoned_meta_io_lock;
spinlock_t treelog_bg_lock;
u64 treelog_bg;
--- a/fs/btrfs/zoned.c
+++ b/fs/btrfs/zoned.c
@@ -386,6 +386,16 @@ int btrfs_get_dev_zone_info(struct btrfs
nr_sectors = bdev_nr_sectors(bdev);
zone_info->zone_size_shift = ilog2(zone_info->zone_size);
zone_info->nr_zones = nr_sectors >> ilog2(zone_sectors);
+ /*
+ * We limit max_zone_append_size also by max_segments *
+ * PAGE_SIZE. Technically, we can have multiple pages per segment. But,
+ * since btrfs adds the pages one by one to a bio, and btrfs cannot
+ * increase the metadata reservation even if it increases the number of
+ * extents, it is safe to stick with the limit.
+ */
+ zone_info->max_zone_append_size =
+ min_t(u64, (u64)bdev_max_zone_append_sectors(bdev) << SECTOR_SHIFT,
+ (u64)bdev_max_segments(bdev) << PAGE_SHIFT);
if (!IS_ALIGNED(nr_sectors, zone_sectors))
zone_info->nr_zones++;

@@ -570,6 +580,7 @@ int btrfs_check_zoned_mode(struct btrfs_
u64 zoned_devices = 0;
u64 nr_devices = 0;
u64 zone_size = 0;
+ u64 max_zone_append_size = 0;
const bool incompat_zoned = btrfs_fs_incompat(fs_info, ZONED);
int ret = 0;

@@ -605,6 +616,11 @@ int btrfs_check_zoned_mode(struct btrfs_
ret = -EINVAL;
goto out;
}
+ if (!max_zone_append_size ||
+ (zone_info->max_zone_append_size &&
+ zone_info->max_zone_append_size < max_zone_append_size))
+ max_zone_append_size =
+ zone_info->max_zone_append_size;
}
nr_devices++;
}
@@ -654,6 +670,7 @@ int btrfs_check_zoned_mode(struct btrfs_
}

fs_info->zone_size = zone_size;
+ fs_info->max_zone_append_size = max_zone_append_size;
fs_info->fs_devices->chunk_alloc_policy = BTRFS_CHUNK_ALLOC_ZONED;

/*
--- a/fs/btrfs/zoned.h
+++ b/fs/btrfs/zoned.h
@@ -23,6 +23,7 @@ struct btrfs_zoned_device_info {
*/
u64 zone_size;
u8 zone_size_shift;
+ u64 max_zone_append_size;
u32 nr_zones;
unsigned long *seq_zones;
unsigned long *empty_zones;