[PATCH 15/17] btrfs: calculate file system wide queue limit for zoned mode

Christoph Hellwig
2022-09-01T07:44:13Z

To be able to split a write into properly sized zone append commands,
we need a queue_limits structure that contains the least common
denominator suitable for all devices.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
fs/btrfs/ctree.h | 4 +++-
fs/btrfs/zoned.c | 36 ++++++++++++++++++------------------
fs/btrfs/zoned.h | 1 -
3 files changed, 21 insertions(+), 20 deletions(-)

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 5e57e3c6a1fd6..a37129363e184 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1071,8 +1071,10 @@ struct btrfs_fs_info {
*/
u64 zone_size;

- /* Max size to emit ZONE_APPEND write command */
+ /* Constraints for ZONE_APPEND commands: */
+ struct queue_limits limits;
u64 max_zone_append_size;
+
struct mutex zoned_meta_io_lock;
spinlock_t treelog_bg_lock;
u64 treelog_bg;
diff --git a/fs/btrfs/zoned.c b/fs/btrfs/zoned.c
index 2638f71eec4b6..6e04fbbd76b92 100644
--- a/fs/btrfs/zoned.c
+++ b/fs/btrfs/zoned.c
@@ -415,16 +415,6 @@ int btrfs_get_dev_zone_info(struct btrfs_device *device, bool populate_cache)
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++;

@@ -646,14 +636,16 @@ int btrfs_get_dev_zone(struct btrfs_device *device, u64 pos,
int btrfs_check_zoned_mode(struct btrfs_fs_info *fs_info)
{
struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
+ struct queue_limits *lim = &fs_info->limits;
struct btrfs_device *device;
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;

+ blk_set_stacking_limits(lim);
+
/* Count zoned devices */
list_for_each_entry(device, &fs_devices->devices, dev_list) {
enum blk_zoned_model model;
@@ -685,11 +677,9 @@ int btrfs_check_zoned_mode(struct btrfs_fs_info *fs_info)
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;
+ blk_stack_limits(lim,
+ &bdev_get_queue(device->bdev)->limits,
+ 0);
}
nr_devices++;
}
@@ -739,8 +729,18 @@ int btrfs_check_zoned_mode(struct btrfs_fs_info *fs_info)
}

fs_info->zone_size = zone_size;
- fs_info->max_zone_append_size = ALIGN_DOWN(max_zone_append_size,
- fs_info->sectorsize);
+ /*
+ * Also limit max_zone_append_size 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.
+ */
+ fs_info->max_zone_append_size = ALIGN_DOWN(
+ min3((u64)lim->max_zone_append_sectors << SECTOR_SHIFT,
+ (u64)lim->max_sectors << SECTOR_SHIFT,
+ (u64)lim->max_segments << PAGE_SHIFT),
+ fs_info->sectorsize);
fs_info->fs_devices->chunk_alloc_policy = BTRFS_CHUNK_ALLOC_ZONED;
if (fs_info->max_zone_append_size < fs_info->max_extent_size)
fs_info->max_extent_size = fs_info->max_zone_append_size;
diff --git a/fs/btrfs/zoned.h b/fs/btrfs/zoned.h
index cafa639927050..0f22b22fe359f 100644
--- a/fs/btrfs/zoned.h
+++ b/fs/btrfs/zoned.h
@@ -19,7 +19,6 @@ struct btrfs_zoned_device_info {
*/
u64 zone_size;
u8 zone_size_shift;
- u64 max_zone_append_size;
u32 nr_zones;
unsigned int max_active_zones;
atomic_t active_zones_left;
--
2.30.2