@@ -21,6 +21,58 @@ Description:
device is offset from the internal allocation unit's
natural alignment.
+What: /sys/block/<disk>/atomic_write_max_bytes
+Date: February 2024
+Contact: Himanshu Madhani <himanshu.madhani@oracle.com>
+Description:
+ [RO] This parameter specifies the maximum atomic write
+ size reported by the device. This parameter is relevant
+ for merging of writes, where a merged atomic write
+ operation must not exceed this number of bytes.
+ This parameter may be greater to the value in
+ atomic_write_unit_max_bytes as
+ atomic_write_unit_max_bytes will be rounded down to a
+ power-of-two and atomic_write_unit_max_bytes may also be
+ limited by some other queue limits, such as max_segments.
+ This parameter - along with atomic_write_unit_min_bytes
+ and atomic_write_unit_max_bytes - will not be larger than
+ max_hw_sectors_kb, but may be larger than max_sectors_kb.
+
+
+What: /sys/block/<disk>/atomic_write_unit_min_bytes
+Date: February 2024
+Contact: Himanshu Madhani <himanshu.madhani@oracle.com>
+Description:
+ [RO] This parameter specifies the smallest block which can
+ be written atomically with an atomic write operation. All
+ atomic write operations must begin at a
+ atomic_write_unit_min boundary and must be multiples of
+ atomic_write_unit_min. This value must be a power-of-two.
+
+
+What: /sys/block/<disk>/atomic_write_unit_max_bytes
+Date: February 2024
+Contact: Himanshu Madhani <himanshu.madhani@oracle.com>
+Description:
+ [RO] This parameter defines the largest block which can be
+ written atomically with an atomic write operation. This
+ value must be a multiple of atomic_write_unit_min and must
+ be a power-of-two. This value will not be larger than
+ atomic_write_max_bytes.
+
+
+What: /sys/block/<disk>/atomic_write_boundary_bytes
+Date: February 2024
+Contact: Himanshu Madhani <himanshu.madhani@oracle.com>
+Description:
+ [RO] A device may need to internally split I/Os which
+ straddle a given logical block address boundary. In that
+ case a single atomic write operation will be processed as
+ one of more sub-operations which each complete atomically.
+ This parameter specifies the size in bytes of the atomic
+ boundary if one is reported by the device. This value must
+ be a power-of-two.
+
What: /sys/block/<disk>/diskseq
Date: February 2021
@@ -18,6 +18,46 @@
#include "blk-rq-qos.h"
#include "blk-throttle.h"
+/*
+ * rq_straddles_atomic_write_boundary - check for boundary violation
+ * @rq: request to check
+ * @front: data size to be appended to front
+ * @back: data size to be appended to back
+ *
+ * Determine whether merging a request or bio into another request will result
+ * in a merged request which straddles an atomic write boundary.
+ *
+ * The value @front_adjust is the data which would be appended to the front of
+ * @rq, while the value @back_adjust is the data which would be appended to the
+ * back of @rq. Callers will typically only have either @front_adjust or
+ * @back_adjust as non-zero.
+ *
+ */
+static bool rq_straddles_atomic_write_boundary(struct request *rq,
+ unsigned int front_adjust,
+ unsigned int back_adjust)
+{
+ unsigned int boundary = queue_atomic_write_boundary_bytes(rq->q);
+ u64 mask, start_rq_pos, end_rq_pos;
+
+ if (!boundary)
+ return false;
+
+ start_rq_pos = blk_rq_pos(rq) << SECTOR_SHIFT;
+ end_rq_pos = start_rq_pos + blk_rq_bytes(rq) - 1;
+
+ start_rq_pos -= front_adjust;
+ end_rq_pos += back_adjust;
+
+ mask = ~(boundary - 1);
+
+ /* Top bits are different, so crossed a boundary */
+ if ((start_rq_pos & mask) != (end_rq_pos & mask))
+ return true;
+
+ return false;
+}
+
static inline void bio_get_first_bvec(struct bio *bio, struct bio_vec *bv)
{
*bv = mp_bvec_iter_bvec(bio->bi_io_vec, bio->bi_iter);
@@ -167,7 +207,16 @@ static inline unsigned get_max_io_size(struct bio *bio,
{
unsigned pbs = lim->physical_block_size >> SECTOR_SHIFT;
unsigned lbs = lim->logical_block_size >> SECTOR_SHIFT;
- unsigned max_sectors = lim->max_sectors, start, end;
+ unsigned max_sectors, start, end;
+
+ /*
+ * We ignore lim->max_sectors for atomic writes simply because
+ * it may less than the bio size, which we cannot tolerate.
+ */
+ if (bio->bi_opf & REQ_ATOMIC)
+ max_sectors = lim->atomic_write_max_sectors;
+ else
+ max_sectors = lim->max_sectors;
if (lim->chunk_sectors) {
max_sectors = min(max_sectors,
@@ -305,6 +354,11 @@ struct bio *bio_split_rw(struct bio *bio, const struct queue_limits *lim,
*segs = nsegs;
return NULL;
split:
+ if (bio->bi_opf & REQ_ATOMIC) {
+ bio->bi_status = BLK_STS_IOERR;
+ bio_endio(bio);
+ return ERR_PTR(-EINVAL);
+ }
/*
* We can't sanely support splitting for a REQ_NOWAIT bio. End it
* with EAGAIN if splitting is required and return an error pointer.
@@ -645,6 +699,13 @@ int ll_back_merge_fn(struct request *req, struct bio *bio, unsigned int nr_segs)
return 0;
}
+ if (req->cmd_flags & REQ_ATOMIC) {
+ if (rq_straddles_atomic_write_boundary(req,
+ 0, bio->bi_iter.bi_size)) {
+ return 0;
+ }
+ }
+
return ll_new_hw_segment(req, bio, nr_segs);
}
@@ -664,6 +725,13 @@ static int ll_front_merge_fn(struct request *req, struct bio *bio,
return 0;
}
+ if (req->cmd_flags & REQ_ATOMIC) {
+ if (rq_straddles_atomic_write_boundary(req,
+ bio->bi_iter.bi_size, 0)) {
+ return 0;
+ }
+ }
+
return ll_new_hw_segment(req, bio, nr_segs);
}
@@ -700,6 +768,13 @@ static int ll_merge_requests_fn(struct request_queue *q, struct request *req,
blk_rq_get_max_sectors(req, blk_rq_pos(req)))
return 0;
+ if (req->cmd_flags & REQ_ATOMIC) {
+ if (rq_straddles_atomic_write_boundary(req,
+ 0, blk_rq_bytes(next))) {
+ return 0;
+ }
+ }
+
total_phys_segments = req->nr_phys_segments + next->nr_phys_segments;
if (total_phys_segments > blk_rq_get_max_segments(req))
return 0;
@@ -795,6 +870,18 @@ static enum elv_merge blk_try_req_merge(struct request *req,
return ELEVATOR_NO_MERGE;
}
+static bool blk_atomic_write_mergeable_rq_bio(struct request *rq,
+ struct bio *bio)
+{
+ return (rq->cmd_flags & REQ_ATOMIC) == (bio->bi_opf & REQ_ATOMIC);
+}
+
+static bool blk_atomic_write_mergeable_rqs(struct request *rq,
+ struct request *next)
+{
+ return (rq->cmd_flags & REQ_ATOMIC) == (next->cmd_flags & REQ_ATOMIC);
+}
+
/*
* For non-mq, this has to be called with the request spinlock acquired.
* For mq with scheduling, the appropriate queue wide lock should be held.
@@ -814,6 +901,9 @@ static struct request *attempt_merge(struct request_queue *q,
if (req->ioprio != next->ioprio)
return NULL;
+ if (!blk_atomic_write_mergeable_rqs(req, next))
+ return NULL;
+
/*
* If we are allowed to merge, then append bio list
* from next to rq and release next. merge_requests_fn
@@ -941,6 +1031,9 @@ bool blk_rq_merge_ok(struct request *rq, struct bio *bio)
if (rq->ioprio != bio_prio(bio))
return false;
+ if (blk_atomic_write_mergeable_rq_bio(rq, bio) == false)
+ return false;
+
return true;
}
@@ -59,6 +59,13 @@ void blk_set_default_limits(struct queue_limits *lim)
lim->zoned = false;
lim->zone_write_granularity = 0;
lim->dma_alignment = 511;
+ lim->atomic_write_hw_max_sectors = 0;
+ lim->atomic_write_max_sectors = 0;
+ lim->atomic_write_hw_boundary_sectors = 0;
+ lim->atomic_write_hw_unit_min_sectors = 0;
+ lim->atomic_write_unit_min_sectors = 0;
+ lim->atomic_write_hw_unit_max_sectors = 0;
+ lim->atomic_write_unit_max_sectors = 0;
}
/**
@@ -101,6 +108,43 @@ void blk_queue_bounce_limit(struct request_queue *q, enum blk_bounce bounce)
}
EXPORT_SYMBOL(blk_queue_bounce_limit);
+/*
+ * Returns max guaranteed sectors which we can fit in a bio. For convenience of
+ * users, rounddown_pow_of_two() the return value.
+ *
+ * We always assume that we can fit in at least PAGE_SIZE in a segment, apart
+ * from first and last segments.
+ */
+static
+unsigned int blk_queue_max_guaranteed_bio_sectors(struct queue_limits *limits,
+ struct request_queue *q)
+{
+ unsigned int max_segments = min(BIO_MAX_VECS, limits->max_segments);
+ unsigned int length;
+
+ length = min(max_segments, 2) * queue_logical_block_size(q);
+ if (max_segments > 2)
+ length += (max_segments - 2) * PAGE_SIZE;
+
+ return rounddown_pow_of_two(length >> SECTOR_SHIFT);
+}
+
+static void blk_atomic_writes_update_limits(struct request_queue *q)
+{
+ struct queue_limits *limits = &q->limits;
+ unsigned int max_hw_sectors =
+ rounddown_pow_of_two(limits->max_hw_sectors);
+ unsigned int unit_limit = min(max_hw_sectors,
+ blk_queue_max_guaranteed_bio_sectors(limits, q));
+
+ limits->atomic_write_max_sectors =
+ min(limits->atomic_write_hw_max_sectors, max_hw_sectors);
+ limits->atomic_write_unit_min_sectors =
+ min(limits->atomic_write_hw_unit_min_sectors, unit_limit);
+ limits->atomic_write_unit_max_sectors =
+ min(limits->atomic_write_hw_unit_max_sectors, unit_limit);
+}
+
/**
* blk_queue_max_hw_sectors - set max sectors for a request for this queue
* @q: the request queue for the device
@@ -145,6 +189,8 @@ void blk_queue_max_hw_sectors(struct request_queue *q, unsigned int max_hw_secto
limits->logical_block_size >> SECTOR_SHIFT);
limits->max_sectors = max_sectors;
+ blk_atomic_writes_update_limits(q);
+
if (!q->disk)
return;
q->disk->bdi->io_pages = max_sectors >> (PAGE_SHIFT - 9);
@@ -182,6 +228,61 @@ void blk_queue_max_discard_sectors(struct request_queue *q,
}
EXPORT_SYMBOL(blk_queue_max_discard_sectors);
+/**
+ * blk_queue_atomic_write_max_bytes - set max bytes supported by
+ * the device for atomic write operations.
+ * @q: the request queue for the device
+ * @bytes: maximum bytes supported
+ */
+void blk_queue_atomic_write_max_bytes(struct request_queue *q,
+ unsigned int bytes)
+{
+ q->limits.atomic_write_hw_max_sectors = bytes >> SECTOR_SHIFT;
+ blk_atomic_writes_update_limits(q);
+}
+EXPORT_SYMBOL(blk_queue_atomic_write_max_bytes);
+
+/**
+ * blk_queue_atomic_write_boundary_bytes - Device's logical block address space
+ * which an atomic write should not cross.
+ * @q: the request queue for the device
+ * @bytes: must be a power-of-two.
+ */
+void blk_queue_atomic_write_boundary_bytes(struct request_queue *q,
+ unsigned int bytes)
+{
+ q->limits.atomic_write_hw_boundary_sectors = bytes >> SECTOR_SHIFT;
+}
+EXPORT_SYMBOL(blk_queue_atomic_write_boundary_bytes);
+
+/**
+ * blk_queue_atomic_write_unit_min_sectors - smallest unit that can be written
+ * atomically to the device.
+ * @q: the request queue for the device
+ * @sectors: must be a power-of-two.
+ */
+void blk_queue_atomic_write_unit_min_sectors(struct request_queue *q,
+ unsigned int sectors)
+{
+ q->limits.atomic_write_hw_unit_min_sectors = sectors;
+ blk_atomic_writes_update_limits(q);
+}
+EXPORT_SYMBOL(blk_queue_atomic_write_unit_min_sectors);
+
+/*
+ * blk_queue_atomic_write_unit_max_sectors - largest unit that can be written
+ * atomically to the device.
+ * @q: the request queue for the device
+ * @sectors: must be a power-of-two.
+ */
+void blk_queue_atomic_write_unit_max_sectors(struct request_queue *q,
+ unsigned int sectors)
+{
+ q->limits.atomic_write_hw_unit_max_sectors = sectors;
+ blk_atomic_writes_update_limits(q);
+}
+EXPORT_SYMBOL(blk_queue_atomic_write_unit_max_sectors);
+
/**
* blk_queue_max_secure_erase_sectors - set max sectors for a secure erase
* @q: the request queue for the device
@@ -118,6 +118,30 @@ static ssize_t queue_max_discard_segments_show(struct request_queue *q,
return queue_var_show(queue_max_discard_segments(q), page);
}
+static ssize_t queue_atomic_write_max_bytes_show(struct request_queue *q,
+ char *page)
+{
+ return queue_var_show(queue_atomic_write_max_bytes(q), page);
+}
+
+static ssize_t queue_atomic_write_boundary_show(struct request_queue *q,
+ char *page)
+{
+ return queue_var_show(queue_atomic_write_boundary_bytes(q), page);
+}
+
+static ssize_t queue_atomic_write_unit_min_show(struct request_queue *q,
+ char *page)
+{
+ return queue_var_show(queue_atomic_write_unit_min_bytes(q), page);
+}
+
+static ssize_t queue_atomic_write_unit_max_show(struct request_queue *q,
+ char *page)
+{
+ return queue_var_show(queue_atomic_write_unit_max_bytes(q), page);
+}
+
static ssize_t queue_max_integrity_segments_show(struct request_queue *q, char *page)
{
return queue_var_show(q->limits.max_integrity_segments, page);
@@ -502,6 +526,11 @@ QUEUE_RO_ENTRY(queue_discard_max_hw, "discard_max_hw_bytes");
QUEUE_RW_ENTRY(queue_discard_max, "discard_max_bytes");
QUEUE_RO_ENTRY(queue_discard_zeroes_data, "discard_zeroes_data");
+QUEUE_RO_ENTRY(queue_atomic_write_max_bytes, "atomic_write_max_bytes");
+QUEUE_RO_ENTRY(queue_atomic_write_boundary, "atomic_write_boundary_bytes");
+QUEUE_RO_ENTRY(queue_atomic_write_unit_max, "atomic_write_unit_max_bytes");
+QUEUE_RO_ENTRY(queue_atomic_write_unit_min, "atomic_write_unit_min_bytes");
+
QUEUE_RO_ENTRY(queue_write_same_max, "write_same_max_bytes");
QUEUE_RO_ENTRY(queue_write_zeroes_max, "write_zeroes_max_bytes");
QUEUE_RO_ENTRY(queue_zone_append_max, "zone_append_max_bytes");
@@ -629,6 +658,10 @@ static struct attribute *queue_attrs[] = {
&queue_discard_max_entry.attr,
&queue_discard_max_hw_entry.attr,
&queue_discard_zeroes_data_entry.attr,
+ &queue_atomic_write_max_bytes_entry.attr,
+ &queue_atomic_write_boundary_entry.attr,
+ &queue_atomic_write_unit_min_entry.attr,
+ &queue_atomic_write_unit_max_entry.attr,
&queue_write_same_max_entry.attr,
&queue_write_zeroes_max_entry.attr,
&queue_zone_append_max_entry.attr,
@@ -178,6 +178,9 @@ static inline unsigned int blk_queue_get_max_sectors(struct request *rq)
if (unlikely(op == REQ_OP_WRITE_ZEROES))
return q->limits.max_write_zeroes_sectors;
+ if (rq->cmd_flags & REQ_ATOMIC)
+ return q->limits.atomic_write_max_sectors;
+
return q->limits.max_sectors;
}
@@ -421,7 +421,7 @@ enum req_flag_bits {
__REQ_SWAP, /* swap I/O */
__REQ_DRV, /* for driver use */
__REQ_FS_PRIVATE, /* for file system (submitter) use */
-
+ __REQ_ATOMIC, /* for atomic write operations */
/*
* Command specific flags, keep last:
*/
@@ -453,6 +453,7 @@ enum req_flag_bits {
#define REQ_SWAP (__force blk_opf_t)(1ULL << __REQ_SWAP)
#define REQ_DRV (__force blk_opf_t)(1ULL << __REQ_DRV)
#define REQ_FS_PRIVATE (__force blk_opf_t)(1ULL << __REQ_FS_PRIVATE)
+#define REQ_ATOMIC (__force blk_opf_t)(1ULL << __REQ_ATOMIC)
#define REQ_NOUNMAP (__force blk_opf_t)(1ULL << __REQ_NOUNMAP)
@@ -299,6 +299,15 @@ struct queue_limits {
unsigned int discard_alignment;
unsigned int zone_write_granularity;
+ /* atomic write limits */
+ unsigned int atomic_write_hw_max_sectors;
+ unsigned int atomic_write_max_sectors;
+ unsigned int atomic_write_hw_boundary_sectors;
+ unsigned int atomic_write_hw_unit_min_sectors;
+ unsigned int atomic_write_unit_min_sectors;
+ unsigned int atomic_write_hw_unit_max_sectors;
+ unsigned int atomic_write_unit_max_sectors;
+
unsigned short max_segments;
unsigned short max_integrity_segments;
unsigned short max_discard_segments;
@@ -885,6 +894,14 @@ void blk_queue_zone_write_granularity(struct request_queue *q,
unsigned int size);
extern void blk_queue_alignment_offset(struct request_queue *q,
unsigned int alignment);
+void blk_queue_atomic_write_max_bytes(struct request_queue *q,
+ unsigned int bytes);
+void blk_queue_atomic_write_unit_max_sectors(struct request_queue *q,
+ unsigned int sectors);
+void blk_queue_atomic_write_unit_min_sectors(struct request_queue *q,
+ unsigned int sectors);
+void blk_queue_atomic_write_boundary_bytes(struct request_queue *q,
+ unsigned int bytes);
void disk_update_readahead(struct gendisk *disk);
extern void blk_limits_io_min(struct queue_limits *limits, unsigned int min);
extern void blk_queue_io_min(struct request_queue *q, unsigned int min);
@@ -1291,6 +1308,30 @@ static inline int queue_dma_alignment(const struct request_queue *q)
return q ? q->limits.dma_alignment : 511;
}
+static inline unsigned int
+queue_atomic_write_unit_max_bytes(const struct request_queue *q)
+{
+ return q->limits.atomic_write_unit_max_sectors << SECTOR_SHIFT;
+}
+
+static inline unsigned int
+queue_atomic_write_unit_min_bytes(const struct request_queue *q)
+{
+ return q->limits.atomic_write_unit_min_sectors << SECTOR_SHIFT;
+}
+
+static inline unsigned int
+queue_atomic_write_boundary_bytes(const struct request_queue *q)
+{
+ return q->limits.atomic_write_hw_boundary_sectors << SECTOR_SHIFT;
+}
+
+static inline unsigned int
+queue_atomic_write_max_bytes(const struct request_queue *q)
+{
+ return q->limits.atomic_write_max_sectors << SECTOR_SHIFT;
+}
+
static inline unsigned int bdev_dma_alignment(struct block_device *bdev)
{
return queue_dma_alignment(bdev_get_queue(bdev));
@@ -1540,6 +1581,26 @@ struct io_comp_batch {
void (*complete)(struct io_comp_batch *);
};
+static inline bool bdev_can_atomic_write(struct block_device *bdev)
+{
+ struct request_queue *bd_queue = bdev->bd_queue;
+ struct queue_limits *limits = &bd_queue->limits;
+
+ if (!limits->atomic_write_unit_min_sectors)
+ return false;
+
+ if (bdev_is_partition(bdev)) {
+ sector_t bd_start_sect = bdev->bd_start_sect;
+ unsigned int align =
+ max(limits->atomic_write_unit_min_sectors,
+ limits->atomic_write_hw_boundary_sectors);
+ if (!IS_ALIGNED(bd_start_sect, align))
+ return false;
+ }
+
+ return true;
+}
+
#define DEFINE_IO_COMP_BATCH(name) struct io_comp_batch name = { }
#endif /* _LINUX_BLKDEV_H */
Add atomic write support, as follows: - add helper functions to get request_queue atomic write limits - report request_queue atomic write support limits to sysfs and update Doc - support to safely merge atomic writes - deal with splitting atomic writes - misc helper functions - add a per-request atomic write flag New request_queue limits are added, as follows: - atomic_write_hw_max_sectors is set by the block driver and is the maximum length of an atomic write which the device may support. It is not necessarily a power-of-2. - atomic_write_max_sectors is derived from atomic_write_hw_max_sectors and max_hw_sectors. It is always a power-of-2. Atomic writes may be merged, and atomic_write_max_sectors would be the limit on a merged atomic write request size. This value is not capped at max_sectors, as the value in max_sectors can be controlled from userspace, and it would only cause trouble if userspace could limit atomic_write_max_sectors and the other atomic write limits. - atomic_write_hw_unit_{min,max}_sectors are set by the block driver and are the min/max length of an atomic write unit which the device may support. They both must be a power-of-2. Typically atomic_write_hw_unit_max_sectors will be the same value as atomic_write_hw_max_sectors. - atomic_write_unit_{min,max}_sectors are derived from atomic_write_hw_unit_{min,max}_sectors, max_hw_sectors, and block core limits. Both min and max values must be a power-of-2. Typically a FS will use these values for reporting atomic write limits in statx. - atomic_write_hw_boundary_sectors is set by the block driver. If non-zero, it indicates an LBA space boundary at which an atomic write straddles no longer is atomically executed by the disk. The value must be a power-of-2. Note that it would be acceptable to enforce a rule that atomic_write_hw_boundary_sectors is a multiple of atomic_write_hw_unit_max, but the resultant code would be more complicated. All atomic writes limits are by default set 0 to indicate no atomic write support. Even though it is assumed by Linux that a logical block can always be atomically written, we ignore this as it is not of particular interest. Stacked devices are just not supported either for now. An atomic write must always be submitted to the block driver as part of a single request. As such, only a single BIO must be submitted to the block layer for an atomic write. When a single atomic write BIO is submitted, it cannot be split. As such, atomic_write_unit_{max, min}_sectors are limited by the maximum guaranteed BIO size which will not be required to be split. This max size is calculated by request_queue max segments and the number of bvecs a BIO can fit, BIO_MAX_VECS. Currently we rely on userspace issuing a write with iovcnt=1 for pwritev2() - and thus we can rely on each segment containing PAGE_SIZE of data, apart from the first+last, which we can only rely on to contain logical block size of data as they are aligned according to direct IO alignment rules. New sysfs files are added to report the following atomic write limits: - atomic_write_unit_max_bytes - same as atomic_write_unit_max_sectors in bytes - atomic_write_unit_min_bytes - same as atomic_write_unit_min_sectors in bytes - atomic_write_boundary_bytes - same as atomic_write_hw_boundary_sectors in bytes - atomic_write_max_bytes - same as atomic_write_max_sectors in bytes Atomic writes may only be merged with other atomic writes and only under the following conditions: - total resultant request length <= atomic_write_max_bytes - the merged write does not straddle a boundary Helper function bdev_can_atomic_write() is added to indicate whether atomic writes may be issued to a bdev. If a bdev is a partition, the partition start must be aligned with both atomic_write_unit_min_sectors and atomic_write_hw_boundary_sectors. Flag REQ_ATOMIC is used for indicating an atomic write. Co-developed-by: Himanshu Madhani <himanshu.madhani@oracle.com> Signed-off-by: Himanshu Madhani <himanshu.madhani@oracle.com> Signed-off-by: John Garry <john.g.garry@oracle.com> --- Documentation/ABI/stable/sysfs-block | 52 ++++++++++++++ block/blk-merge.c | 95 ++++++++++++++++++++++++- block/blk-settings.c | 101 +++++++++++++++++++++++++++ block/blk-sysfs.c | 33 +++++++++ block/blk.h | 3 + include/linux/blk_types.h | 3 +- include/linux/blkdev.h | 61 ++++++++++++++++ 7 files changed, 346 insertions(+), 2 deletions(-)