[PATCH 03/15] block: add an API to atomically update queue limits

Christoph Hellwig
2024-01-22T17:37:00Z

Add a new queue_limits_{start,commit}_update pair of functions that
allows taking an atomic snapshot of queue limits, update it, and
commit it if it passes validity checking.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
block/blk-core.c | 1 +
block/blk-settings.c | 140 +++++++++++++++++++++++++++++++++++++++++
block/blk.h | 1 +
include/linux/blkdev.h | 23 +++++++
4 files changed, 165 insertions(+)

diff --git a/block/blk-core.c b/block/blk-core.c
index 11342af420d0c4..09f4a44a4aa3cc 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -424,6 +424,7 @@ struct request_queue *blk_alloc_queue(int node_id)
mutex_init(&q->debugfs_mutex);
mutex_init(&q->sysfs_lock);
mutex_init(&q->sysfs_dir_lock);
+ mutex_init(&q->limits_lock);
mutex_init(&q->rq_qos_mutex);
spin_lock_init(&q->queue_lock);

diff --git a/block/blk-settings.c b/block/blk-settings.c
index e872b0e168525e..b6692143ccf034 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -96,6 +96,146 @@ static void blk_apply_bdi_limits(struct backing_dev_info *bdi,
bdi->io_pages = lim->max_sectors >> (PAGE_SHIFT - 9);
}

+static int blk_validate_zoned_limits(struct queue_limits *lim)
+{
+ if (!lim->zoned) {
+ if (WARN_ON_ONCE(lim->max_open_zones) ||
+ WARN_ON_ONCE(lim->max_active_zones) ||
+ WARN_ON_ONCE(lim->zone_write_granularity) ||
+ WARN_ON_ONCE(lim->max_zone_append_sectors))
+ return -EINVAL;
+ return 0;
+ }
+
+ if (WARN_ON_ONCE(!IS_ENABLED(CONFIG_BLK_DEV_ZONED)))
+ return -EINVAL;
+
+ if (lim->zone_write_granularity < lim->logical_block_size)
+ lim->zone_write_granularity = lim->logical_block_size;
+
+ if (lim->max_zone_append_sectors) {
+ if (WARN_ON_ONCE(!lim->chunk_sectors))
+ return -EINVAL;
+ lim->max_zone_append_sectors =
+ min3(lim->max_hw_sectors,
+ lim->max_zone_append_sectors,
+ lim->chunk_sectors);
+ }
+
+ return 0;
+}
+
+int blk_validate_limits(struct queue_limits *lim)
+{
+ unsigned int max_hw_sectors;
+
+ if (!lim->logical_block_size)
+ lim->logical_block_size = SECTOR_SIZE;
+
+ if (!lim->physical_block_size)
+ lim->physical_block_size = SECTOR_SIZE;
+ if (lim->physical_block_size < lim->logical_block_size)
+ lim->physical_block_size = lim->physical_block_size;
+
+ if (!lim->io_min)
+ lim->io_min = SECTOR_SIZE;
+ if (lim->io_min < lim->physical_block_size)
+ lim->io_min = lim->physical_block_size;
+
+ if (!lim->max_hw_sectors)
+ lim->max_hw_sectors = BLK_SAFE_MAX_SECTORS;
+ if (WARN_ON_ONCE(lim->max_hw_sectors < PAGE_SIZE / SECTOR_SIZE))
+ return -EINVAL;
+
+ lim->max_hw_sectors = round_down(lim->max_hw_sectors,
+ lim->logical_block_size >> SECTOR_SHIFT);
+
+ max_hw_sectors = min_not_zero(lim->max_hw_sectors,
+ lim->max_dev_sectors);
+ if (lim->max_user_sectors) {
+ if (lim->max_user_sectors > max_hw_sectors ||
+ lim->max_user_sectors < PAGE_SIZE / SECTOR_SIZE)
+ return -EINVAL;
+ lim->max_sectors = min(max_hw_sectors, lim->max_user_sectors);
+ } else {
+ lim->max_sectors = min(max_hw_sectors, BLK_DEF_MAX_SECTORS_CAP);
+ }
+
+ lim->max_sectors = round_down(lim->max_sectors,
+ lim->logical_block_size >> SECTOR_SHIFT);
+
+ if (!lim->max_segments)
+ lim->max_segments = BLK_MAX_SEGMENTS;
+
+ lim->max_discard_sectors = lim->max_hw_discard_sectors;
+ if (!lim->max_discard_segments)
+ lim->max_discard_segments = 1;
+
+ if (lim->discard_granularity < lim->physical_block_size)
+ lim->discard_granularity = lim->physical_block_size;
+
+ if (!lim->seg_boundary_mask)
+ lim->seg_boundary_mask = BLK_SEG_BOUNDARY_MASK;
+ if (WARN_ON_ONCE(lim->seg_boundary_mask < PAGE_SIZE - 1))
+ return -EINVAL;
+
+ if (!lim->max_segment_size)
+ lim->max_segment_size = BLK_MAX_SEGMENT_SIZE;
+ if (WARN_ON_ONCE(lim->max_segment_size < PAGE_SIZE))
+ return -EINVAL;
+
+ /*
+ * Devices that require a virtual boundary do not support scatter/gather
+ * I/O natively, but instead require a descriptor list entry for each
+ * page (which might not be idential to the Linux PAGE_SIZE). Because
+ * of that they are not limited by our notion of "segment size".
+ */
+ if (lim->virt_boundary_mask) {
+ if (WARN_ON_ONCE(lim->max_segment_size &&
+ lim->max_segment_size != UINT_MAX))
+ return -EINVAL;
+ lim->max_segment_size = UINT_MAX;
+ }
+
+ if (!lim->dma_alignment)
+ lim->dma_alignment = SECTOR_SIZE - 1;
+ if (WARN_ON_ONCE(lim->dma_alignment > PAGE_SIZE))
+ return -EINVAL;
+
+ if (lim->alignment_offset) {
+ lim->alignment_offset &= (lim->physical_block_size - 1);
+ lim->misaligned = 0;
+ }
+
+ return blk_validate_zoned_limits(lim);
+}
+
+/**
+ * queue_limits_commit_update - commit an atomic update of queue limits
+ * @q: queue to update
+ * @lim: limits to apply
+ *
+ * Apply the limits in @lim that were obtained from queue_limits_start_update()
+ * and updated by the caller to @q.
+ *
+ * Returns 0 if successful, else a negative error code.
+ */
+int queue_limits_commit_update(struct request_queue *q,
+ struct queue_limits *lim)
+ __releases(q->limits_lock)
+{
+ int error = blk_validate_limits(lim);
+
+ if (!error) {
+ q->limits = *lim;
+ if (q->disk)
+ blk_apply_bdi_limits(q->disk->bdi, lim);
+ }
+ mutex_unlock(&q->limits_lock);
+ return error;
+}
+EXPORT_SYMBOL_GPL(queue_limits_commit_update);
+
/**
* blk_queue_bounce_limit - set bounce buffer limit for queue
* @q: the request queue for the device
diff --git a/block/blk.h b/block/blk.h
index 1ef920f72e0f87..58b5dbac2a487d 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -447,6 +447,7 @@ static inline void bio_release_page(struct bio *bio, struct page *page)
unpin_user_page(page);
}

+int blk_validate_limits(struct queue_limits *lim);
struct request_queue *blk_alloc_queue(int node_id);

int disk_scan_partitions(struct gendisk *disk, blk_mode_t mode);
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 4a2e82c7971c86..5b5d3b238de1e7 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -473,6 +473,7 @@ struct request_queue {

struct mutex sysfs_lock;
struct mutex sysfs_dir_lock;
+ struct mutex limits_lock;

/*
* for reusing dead hctx instance in case of updating
@@ -861,6 +862,28 @@ static inline unsigned int blk_chunk_sectors_left(sector_t offset,
return chunk_sectors - (offset & (chunk_sectors - 1));
}

+/**
+ * queue_limits_start_update - start an atomic update of queue limits
+ * @q: queue to update
+ *
+ * This functions starts an atomic update of the queue limits. It takes a lock
+ * to prevent other updates and returns a snapshot of the current limits that
+ * the caller can modify. The caller must call queue_limits_commit_update()
+ * to finish the update.
+ *
+ * Context: process context. The caller must have frozen the queue or ensured
+ * that there is outstanding I/O by other means.
+ */
+static inline struct queue_limits
+queue_limits_start_update(struct request_queue *q)
+ __acquires(q->limits_lock)
+{
+ mutex_lock(&q->limits_lock);
+ return q->limits;
+}
+int queue_limits_commit_update(struct request_queue *q,
+ struct queue_limits *lim);
+
/*
* Access functions for manipulating queue properties
*/
--
2.39.2