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dm-table: atomic writes support

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Support stacking atomic write limits for DM devices.

All the pre-existing code in blk_stack_atomic_writes_limits() already takes
care of finding the aggregrate limits from the bottom devices.

Feature flag DM_TARGET_ATOMIC_WRITES is introduced so that atomic writes
can be enabled on personalities selectively. This is to ensure that atomic
writes are only enabled when verified to be working properly (for a
specific personality). In addition, it just may not make sense to enable
atomic writes on some personalities (so this flag also helps there).

Signed-off-by: John Garry <john.g.garry@oracle.com>
Reviewed-by: Mike Snitzer <snitzer@kernel.org>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
This commit is contained in:
John Garry 2025-01-16 17:02:56 +00:00 committed by Mikulas Patocka
parent a38425935f
commit 3194e36488
3 changed files with 34 additions and 2 deletions
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29
drivers/md/dm-table.c
View File

@ -1806,6 +1806,32 @@ static bool dm_table_supports_secure_erase(struct dm_table *t)
return true;
}
static int device_not_atomic_write_capable(struct dm_target *ti,
struct dm_dev *dev, sector_t start,
sector_t len, void *data)
{
return !bdev_can_atomic_write(dev->bdev);
}
static bool dm_table_supports_atomic_writes(struct dm_table *t)
{
for (unsigned int i = 0; i < t->num_targets; i++) {
struct dm_target *ti = dm_table_get_target(t, i);
if (!dm_target_supports_atomic_writes(ti->type))
return false;
if (!ti->type->iterate_devices)
return false;
if (ti->type->iterate_devices(ti,
device_not_atomic_write_capable, NULL)) {
return false;
}
}
return true;
}
int dm_table_set_restrictions(struct dm_table *t, struct request_queue *q,
struct queue_limits *limits)
{
@ -1854,6 +1880,9 @@ int dm_table_set_restrictions(struct dm_table *t, struct request_queue *q,
return r;
}
if (dm_table_supports_atomic_writes(t))
limits->features |= BLK_FEAT_ATOMIC_WRITES;
r = queue_limits_set(q, limits);
if (r)
return r;

3
include/linux/device-mapper.h
View File

@ -299,6 +299,9 @@ struct target_type {
#define dm_target_supports_mixed_zoned_model(type) (false)
#endif
#define DM_TARGET_ATOMIC_WRITES 0x00000400
#define dm_target_supports_atomic_writes(type) ((type)->features & DM_TARGET_ATOMIC_WRITES)
struct dm_target {
struct dm_table *table;
struct target_type *type;

4
include/uapi/linux/dm-ioctl.h
View File

@ -286,9 +286,9 @@ enum {
#define DM_DEV_SET_GEOMETRY _IOWR(DM_IOCTL, DM_DEV_SET_GEOMETRY_CMD, struct dm_ioctl)
#define DM_VERSION_MAJOR 4
#define DM_VERSION_MINOR 48
#define DM_VERSION_MINOR 49
#define DM_VERSION_PATCHLEVEL 0
#define DM_VERSION_EXTRA "-ioctl (2023-03-01)"
#define DM_VERSION_EXTRA "-ioctl (2025-01-17)"
/* Status bits */
#define DM_READONLY_FLAG (1 << 0) /* In/Out */