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dm: introduce dm_{get,put}_live_table_bio called from dm_submit_bio 

If a bio is marked REQ_NOWAIT optimize dm_submit_bio()'s dm_table RCU
usage to dm_{get,put}_live_table_fast.

DM core offers protection against blocking (via suspend) if REQ_NOWAIT.

Signed-off-by: Mike Snitzer <snitzer@kernel.org>
This commit is contained in:
Mike Snitzer 2022-03-26 21:08:36 -04:00
parent 982b48ae25
commit 563a225c9f
1 changed files with 24 additions and 4 deletions
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28
drivers/md/dm.c
View File

@ -661,14 +661,16 @@ static void queue_io(struct mapped_device *md, struct bio *bio)
* function to access the md->map field, and make sure they call
* dm_put_live_table() when finished.
*/
struct dm_table *dm_get_live_table(struct mapped_device *md, int *srcu_idx) __acquires(md->io_barrier)
struct dm_table *dm_get_live_table(struct mapped_device *md,
int *srcu_idx) __acquires(md->io_barrier)
{
*srcu_idx = srcu_read_lock(&md->io_barrier);
return srcu_dereference(md->map, &md->io_barrier);
}
void dm_put_live_table(struct mapped_device *md, int srcu_idx) __releases(md->io_barrier)
void dm_put_live_table(struct mapped_device *md,
int srcu_idx) __releases(md->io_barrier)
{
srcu_read_unlock(&md->io_barrier, srcu_idx);
}
@ -694,6 +696,24 @@ static void dm_put_live_table_fast(struct mapped_device *md) __releases(RCU)
rcu_read_unlock();
}
static inline struct dm_table *dm_get_live_table_bio(struct mapped_device *md,
int *srcu_idx, struct bio *bio)
{
if (bio->bi_opf & REQ_NOWAIT)
return dm_get_live_table_fast(md);
else
return dm_get_live_table(md, srcu_idx);
}
static inline void dm_put_live_table_bio(struct mapped_device *md, int srcu_idx,
struct bio *bio)
{
if (bio->bi_opf & REQ_NOWAIT)
dm_put_live_table_fast(md);
else
dm_put_live_table(md, srcu_idx);
}
static char *_dm_claim_ptr = "I belong to device-mapper";
/*
@ -1612,7 +1632,7 @@ static void dm_submit_bio(struct bio *bio)
int srcu_idx;
struct dm_table *map;
map = dm_get_live_table(md, &srcu_idx);
map = dm_get_live_table_bio(md, &srcu_idx, bio);
/* If suspended, or map not yet available, queue this IO for later */
if (unlikely(test_bit(DMF_BLOCK_IO_FOR_SUSPEND, &md->flags)) ||
@ -1635,7 +1655,7 @@ static void dm_submit_bio(struct bio *bio)
dm_split_and_process_bio(md, map, bio);
out:
dm_put_live_table(md, srcu_idx);
dm_put_live_table_bio(md, srcu_idx, bio);
}
static bool dm_poll_dm_io(struct dm_io *io, struct io_comp_batch *iob,