Commit c72758f3 authored by Martin K. Petersen's avatar Martin K. Petersen Committed by Jens Axboe

block: Export I/O topology for block devices and partitions

To support devices with physical block sizes bigger than 512 bytes we
need to ensure proper alignment.  This patch adds support for exposing
I/O topology characteristics as devices are stacked.

  logical_block_size is the smallest unit the device can address.

  physical_block_size indicates the smallest I/O the device can write
  without incurring a read-modify-write penalty.

  The io_min parameter is the smallest preferred I/O size reported by
  the device.  In many cases this is the same as the physical block
  size.  However, the io_min parameter can be scaled up when stacking
  (RAID5 chunk size > physical block size).

  The io_opt characteristic indicates the optimal I/O size reported by
  the device.  This is usually the stripe width for arrays.

  The alignment_offset parameter indicates the number of bytes the start
  of the device/partition is offset from the device's natural alignment.
  Partition tools and MD/DM utilities can use this to pad their offsets
  so filesystems start on proper boundaries.
Signed-off-by: default avatarMartin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
parent cd43e26f
......@@ -60,3 +60,62 @@ Description:
Indicates whether the block layer should automatically
generate checksums for write requests bound for
devices that support receiving integrity metadata.
What: /sys/block/<disk>/alignment_offset
Date: April 2009
Contact: Martin K. Petersen <martin.petersen@oracle.com>
Description:
Storage devices may report a physical block size that is
bigger than the logical block size (for instance a drive
with 4KB physical sectors exposing 512-byte logical
blocks to the operating system). This parameter
indicates how many bytes the beginning of the device is
offset from the disk's natural alignment.
What: /sys/block/<disk>/<partition>/alignment_offset
Date: April 2009
Contact: Martin K. Petersen <martin.petersen@oracle.com>
Description:
Storage devices may report a physical block size that is
bigger than the logical block size (for instance a drive
with 4KB physical sectors exposing 512-byte logical
blocks to the operating system). This parameter
indicates how many bytes the beginning of the partition
is offset from the disk's natural alignment.
What: /sys/block/<disk>/queue/logical_block_size
Date: May 2009
Contact: Martin K. Petersen <martin.petersen@oracle.com>
Description:
This is the smallest unit the storage device can
address. It is typically 512 bytes.
What: /sys/block/<disk>/queue/physical_block_size
Date: May 2009
Contact: Martin K. Petersen <martin.petersen@oracle.com>
Description:
This is the smallest unit the storage device can write
without resorting to read-modify-write operation. It is
usually the same as the logical block size but may be
bigger. One example is SATA drives with 4KB sectors
that expose a 512-byte logical block size to the
operating system.
What: /sys/block/<disk>/queue/minimum_io_size
Date: April 2009
Contact: Martin K. Petersen <martin.petersen@oracle.com>
Description:
Storage devices may report a preferred minimum I/O size,
which is the smallest request the device can perform
without incurring a read-modify-write penalty. For disk
drives this is often the physical block size. For RAID
arrays it is often the stripe chunk size.
What: /sys/block/<disk>/queue/optimal_io_size
Date: April 2009
Contact: Martin K. Petersen <martin.petersen@oracle.com>
Description:
Storage devices may report an optimal I/O size, which is
the device's preferred unit of receiving I/O. This is
rarely reported for disk drives. For RAID devices it is
usually the stripe width or the internal block size.
......@@ -309,9 +309,94 @@ EXPORT_SYMBOL(blk_queue_max_segment_size);
void blk_queue_logical_block_size(struct request_queue *q, unsigned short size)
{
q->limits.logical_block_size = size;
if (q->limits.physical_block_size < size)
q->limits.physical_block_size = size;
if (q->limits.io_min < q->limits.physical_block_size)
q->limits.io_min = q->limits.physical_block_size;
}
EXPORT_SYMBOL(blk_queue_logical_block_size);
/**
* blk_queue_physical_block_size - set physical block size for the queue
* @q: the request queue for the device
* @size: the physical block size, in bytes
*
* Description:
* This should be set to the lowest possible sector size that the
* hardware can operate on without reverting to read-modify-write
* operations.
*/
void blk_queue_physical_block_size(struct request_queue *q, unsigned short size)
{
q->limits.physical_block_size = size;
if (q->limits.physical_block_size < q->limits.logical_block_size)
q->limits.physical_block_size = q->limits.logical_block_size;
if (q->limits.io_min < q->limits.physical_block_size)
q->limits.io_min = q->limits.physical_block_size;
}
EXPORT_SYMBOL(blk_queue_physical_block_size);
/**
* blk_queue_alignment_offset - set physical block alignment offset
* @q: the request queue for the device
* @alignment: alignment offset in bytes
*
* Description:
* Some devices are naturally misaligned to compensate for things like
* the legacy DOS partition table 63-sector offset. Low-level drivers
* should call this function for devices whose first sector is not
* naturally aligned.
*/
void blk_queue_alignment_offset(struct request_queue *q, unsigned int offset)
{
q->limits.alignment_offset =
offset & (q->limits.physical_block_size - 1);
q->limits.misaligned = 0;
}
EXPORT_SYMBOL(blk_queue_alignment_offset);
/**
* blk_queue_io_min - set minimum request size for the queue
* @q: the request queue for the device
* @io_min: smallest I/O size in bytes
*
* Description:
* Some devices have an internal block size bigger than the reported
* hardware sector size. This function can be used to signal the
* smallest I/O the device can perform without incurring a performance
* penalty.
*/
void blk_queue_io_min(struct request_queue *q, unsigned int min)
{
q->limits.io_min = min;
if (q->limits.io_min < q->limits.logical_block_size)
q->limits.io_min = q->limits.logical_block_size;
if (q->limits.io_min < q->limits.physical_block_size)
q->limits.io_min = q->limits.physical_block_size;
}
EXPORT_SYMBOL(blk_queue_io_min);
/**
* blk_queue_io_opt - set optimal request size for the queue
* @q: the request queue for the device
* @io_opt: optimal request size in bytes
*
* Description:
* Drivers can call this function to set the preferred I/O request
* size for devices that report such a value.
*/
void blk_queue_io_opt(struct request_queue *q, unsigned int opt)
{
q->limits.io_opt = opt;
}
EXPORT_SYMBOL(blk_queue_io_opt);
/*
* Returns the minimum that is _not_ zero, unless both are zero.
*/
......@@ -357,6 +442,107 @@ void blk_queue_stack_limits(struct request_queue *t, struct request_queue *b)
}
EXPORT_SYMBOL(blk_queue_stack_limits);
/**
* blk_stack_limits - adjust queue_limits for stacked devices
* @t: the stacking driver limits (top)
* @bdev: the underlying queue limits (bottom)
* @offset: offset to beginning of data within component device
*
* Description:
* Merges two queue_limit structs. Returns 0 if alignment didn't
* change. Returns -1 if adding the bottom device caused
* misalignment.
*/
int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
sector_t offset)
{
t->max_sectors = min_not_zero(t->max_sectors, b->max_sectors);
t->max_hw_sectors = min_not_zero(t->max_hw_sectors, b->max_hw_sectors);
t->seg_boundary_mask = min_not_zero(t->seg_boundary_mask,
b->seg_boundary_mask);
t->max_phys_segments = min_not_zero(t->max_phys_segments,
b->max_phys_segments);
t->max_hw_segments = min_not_zero(t->max_hw_segments,
b->max_hw_segments);
t->max_segment_size = min_not_zero(t->max_segment_size,
b->max_segment_size);
t->logical_block_size = max(t->logical_block_size,
b->logical_block_size);
t->physical_block_size = max(t->physical_block_size,
b->physical_block_size);
t->io_min = max(t->io_min, b->io_min);
t->no_cluster |= b->no_cluster;
/* Bottom device offset aligned? */
if (offset &&
(offset & (b->physical_block_size - 1)) != b->alignment_offset) {
t->misaligned = 1;
return -1;
}
/* If top has no alignment offset, inherit from bottom */
if (!t->alignment_offset)
t->alignment_offset =
b->alignment_offset & (b->physical_block_size - 1);
/* Top device aligned on logical block boundary? */
if (t->alignment_offset & (t->logical_block_size - 1)) {
t->misaligned = 1;
return -1;
}
return 0;
}
/**
* disk_stack_limits - adjust queue limits for stacked drivers
* @t: MD/DM gendisk (top)
* @bdev: the underlying block device (bottom)
* @offset: offset to beginning of data within component device
*
* Description:
* Merges the limits for two queues. Returns 0 if alignment
* didn't change. Returns -1 if adding the bottom device caused
* misalignment.
*/
void disk_stack_limits(struct gendisk *disk, struct block_device *bdev,
sector_t offset)
{
struct request_queue *t = disk->queue;
struct request_queue *b = bdev_get_queue(bdev);
offset += get_start_sect(bdev) << 9;
if (blk_stack_limits(&t->limits, &b->limits, offset) < 0) {
char top[BDEVNAME_SIZE], bottom[BDEVNAME_SIZE];
disk_name(disk, 0, top);
bdevname(bdev, bottom);
printk(KERN_NOTICE "%s: Warning: Device %s is misaligned\n",
top, bottom);
}
if (!t->queue_lock)
WARN_ON_ONCE(1);
else if (!test_bit(QUEUE_FLAG_CLUSTER, &b->queue_flags)) {
unsigned long flags;
spin_lock_irqsave(t->queue_lock, flags);
if (!test_bit(QUEUE_FLAG_CLUSTER, &b->queue_flags))
queue_flag_clear(QUEUE_FLAG_CLUSTER, t);
spin_unlock_irqrestore(t->queue_lock, flags);
}
}
EXPORT_SYMBOL(disk_stack_limits);
/**
* blk_queue_dma_pad - set pad mask
* @q: the request queue for the device
......
......@@ -105,6 +105,21 @@ static ssize_t queue_logical_block_size_show(struct request_queue *q, char *page
return queue_var_show(queue_logical_block_size(q), page);
}
static ssize_t queue_physical_block_size_show(struct request_queue *q, char *page)
{
return queue_var_show(queue_physical_block_size(q), page);
}
static ssize_t queue_io_min_show(struct request_queue *q, char *page)
{
return queue_var_show(queue_io_min(q), page);
}
static ssize_t queue_io_opt_show(struct request_queue *q, char *page)
{
return queue_var_show(queue_io_opt(q), page);
}
static ssize_t
queue_max_sectors_store(struct request_queue *q, const char *page, size_t count)
{
......@@ -257,6 +272,21 @@ static struct queue_sysfs_entry queue_logical_block_size_entry = {
.show = queue_logical_block_size_show,
};
static struct queue_sysfs_entry queue_physical_block_size_entry = {
.attr = {.name = "physical_block_size", .mode = S_IRUGO },
.show = queue_physical_block_size_show,
};
static struct queue_sysfs_entry queue_io_min_entry = {
.attr = {.name = "minimum_io_size", .mode = S_IRUGO },
.show = queue_io_min_show,
};
static struct queue_sysfs_entry queue_io_opt_entry = {
.attr = {.name = "optimal_io_size", .mode = S_IRUGO },
.show = queue_io_opt_show,
};
static struct queue_sysfs_entry queue_nonrot_entry = {
.attr = {.name = "rotational", .mode = S_IRUGO | S_IWUSR },
.show = queue_nonrot_show,
......@@ -289,6 +319,9 @@ static struct attribute *default_attrs[] = {
&queue_iosched_entry.attr,
&queue_hw_sector_size_entry.attr,
&queue_logical_block_size_entry.attr,
&queue_physical_block_size_entry.attr,
&queue_io_min_entry.attr,
&queue_io_opt_entry.attr,
&queue_nonrot_entry.attr,
&queue_nomerges_entry.attr,
&queue_rq_affinity_entry.attr,
......
......@@ -852,11 +852,21 @@ static ssize_t disk_capability_show(struct device *dev,
return sprintf(buf, "%x\n", disk->flags);
}
static ssize_t disk_alignment_offset_show(struct device *dev,
struct device_attribute *attr,
char *buf)
{
struct gendisk *disk = dev_to_disk(dev);
return sprintf(buf, "%d\n", queue_alignment_offset(disk->queue));
}
static DEVICE_ATTR(range, S_IRUGO, disk_range_show, NULL);
static DEVICE_ATTR(ext_range, S_IRUGO, disk_ext_range_show, NULL);
static DEVICE_ATTR(removable, S_IRUGO, disk_removable_show, NULL);
static DEVICE_ATTR(ro, S_IRUGO, disk_ro_show, NULL);
static DEVICE_ATTR(size, S_IRUGO, part_size_show, NULL);
static DEVICE_ATTR(alignment_offset, S_IRUGO, disk_alignment_offset_show, NULL);
static DEVICE_ATTR(capability, S_IRUGO, disk_capability_show, NULL);
static DEVICE_ATTR(stat, S_IRUGO, part_stat_show, NULL);
#ifdef CONFIG_FAIL_MAKE_REQUEST
......@@ -875,6 +885,7 @@ static struct attribute *disk_attrs[] = {
&dev_attr_removable.attr,
&dev_attr_ro.attr,
&dev_attr_size.attr,
&dev_attr_alignment_offset.attr,
&dev_attr_capability.attr,
&dev_attr_stat.attr,
#ifdef CONFIG_FAIL_MAKE_REQUEST
......
......@@ -219,6 +219,13 @@ ssize_t part_size_show(struct device *dev,
return sprintf(buf, "%llu\n",(unsigned long long)p->nr_sects);
}
ssize_t part_alignment_offset_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
struct hd_struct *p = dev_to_part(dev);
return sprintf(buf, "%llu\n", (unsigned long long)p->alignment_offset);
}
ssize_t part_stat_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
......@@ -272,6 +279,7 @@ ssize_t part_fail_store(struct device *dev,
static DEVICE_ATTR(partition, S_IRUGO, part_partition_show, NULL);
static DEVICE_ATTR(start, S_IRUGO, part_start_show, NULL);
static DEVICE_ATTR(size, S_IRUGO, part_size_show, NULL);
static DEVICE_ATTR(alignment_offset, S_IRUGO, part_alignment_offset_show, NULL);
static DEVICE_ATTR(stat, S_IRUGO, part_stat_show, NULL);
#ifdef CONFIG_FAIL_MAKE_REQUEST
static struct device_attribute dev_attr_fail =
......@@ -282,6 +290,7 @@ static struct attribute *part_attrs[] = {
&dev_attr_partition.attr,
&dev_attr_start.attr,
&dev_attr_size.attr,
&dev_attr_alignment_offset.attr,
&dev_attr_stat.attr,
#ifdef CONFIG_FAIL_MAKE_REQUEST
&dev_attr_fail.attr,
......@@ -383,6 +392,7 @@ struct hd_struct *add_partition(struct gendisk *disk, int partno,
pdev = part_to_dev(p);
p->start_sect = start;
p->alignment_offset = queue_sector_alignment_offset(disk->queue, start);
p->nr_sects = len;
p->partno = partno;
p->policy = get_disk_ro(disk);
......
......@@ -314,11 +314,16 @@ struct queue_limits {
unsigned int max_hw_sectors;
unsigned int max_sectors;
unsigned int max_segment_size;
unsigned int physical_block_size;
unsigned int alignment_offset;
unsigned int io_min;
unsigned int io_opt;
unsigned short logical_block_size;
unsigned short max_hw_segments;
unsigned short max_phys_segments;
unsigned char misaligned;
unsigned char no_cluster;
};
......@@ -911,6 +916,15 @@ extern void blk_queue_max_phys_segments(struct request_queue *, unsigned short);
extern void blk_queue_max_hw_segments(struct request_queue *, unsigned short);
extern void blk_queue_max_segment_size(struct request_queue *, unsigned int);
extern void blk_queue_logical_block_size(struct request_queue *, unsigned short);
extern void blk_queue_physical_block_size(struct request_queue *, unsigned short);
extern void blk_queue_alignment_offset(struct request_queue *q,
unsigned int alignment);
extern void blk_queue_io_min(struct request_queue *q, unsigned int min);
extern void blk_queue_io_opt(struct request_queue *q, unsigned int opt);
extern int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
sector_t offset);
extern void disk_stack_limits(struct gendisk *disk, struct block_device *bdev,
sector_t offset);
extern void blk_queue_stack_limits(struct request_queue *t, struct request_queue *b);
extern void blk_queue_dma_pad(struct request_queue *, unsigned int);
extern void blk_queue_update_dma_pad(struct request_queue *, unsigned int);
......@@ -1047,6 +1061,39 @@ static inline unsigned short bdev_logical_block_size(struct block_device *bdev)
return queue_logical_block_size(bdev_get_queue(bdev));
}
static inline unsigned int queue_physical_block_size(struct request_queue *q)
{
return q->limits.physical_block_size;
}
static inline unsigned int queue_io_min(struct request_queue *q)
{
return q->limits.io_min;
}
static inline unsigned int queue_io_opt(struct request_queue *q)
{
return q->limits.io_opt;
}
static inline int queue_alignment_offset(struct request_queue *q)
{
if (q && q->limits.misaligned)
return -1;
if (q && q->limits.alignment_offset)
return q->limits.alignment_offset;
return 0;
}
static inline int queue_sector_alignment_offset(struct request_queue *q,
sector_t sector)
{
return ((sector << 9) - q->limits.alignment_offset)
& (q->limits.io_min - 1);
}
static inline int queue_dma_alignment(struct request_queue *q)
{
return q ? q->dma_alignment : 511;
......
......@@ -90,6 +90,7 @@ struct disk_stats {
struct hd_struct {
sector_t start_sect;
sector_t nr_sects;
sector_t alignment_offset;
struct device __dev;
struct kobject *holder_dir;
int policy, partno;
......
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