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dm snapshot: introduce account_start_copy() and account_end_copy()

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This simple refactoring moves code for modifying the semaphore cow_count
into separate functions to prepare for changes that will extend these
methods to provide for a more sophisticated mechanism for COW
throttling.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Reviewed-by: Nikos Tsironis <ntsironis@arrikto.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This commit is contained in:
Mikulas Patocka 2019-10-02 06:14:17 -04:00 committed by Mike Snitzer
parent 0a005856d3
commit a2f83e8b0c
1 changed files with 15 additions and 5 deletions
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20
drivers/md/dm-snap.c
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@ -1512,6 +1512,16 @@ static void snapshot_dtr(struct dm_target *ti)
kfree(s);
}
static void account_start_copy(struct dm_snapshot *s)
{
down(&s->cow_count);
}
static void account_end_copy(struct dm_snapshot *s)
{
up(&s->cow_count);
}
/*
* Flush a list of buffers.
*/
@ -1732,7 +1742,7 @@ static void copy_callback(int read_err, unsigned long write_err, void *context)
rb_link_node(&pe->out_of_order_node, parent, p);
rb_insert_color(&pe->out_of_order_node, &s->out_of_order_tree);
}
up(&s->cow_count);
account_end_copy(s);
}
/*
@ -1756,7 +1766,7 @@ static void start_copy(struct dm_snap_pending_exception *pe)
dest.count = src.count;
/* Hand over to kcopyd */
down(&s->cow_count);
account_start_copy(s);
dm_kcopyd_copy(s->kcopyd_client, &src, 1, &dest, 0, copy_callback, pe);
}
@ -1776,7 +1786,7 @@ static void start_full_bio(struct dm_snap_pending_exception *pe,
pe->full_bio = bio;
pe->full_bio_end_io = bio->bi_end_io;
down(&s->cow_count);
account_start_copy(s);
callback_data = dm_kcopyd_prepare_callback(s->kcopyd_client,
copy_callback, pe);
@ -1866,7 +1876,7 @@ static void zero_callback(int read_err, unsigned long write_err, void *context)
struct bio *bio = context;
struct dm_snapshot *s = bio->bi_private;
up(&s->cow_count);
account_end_copy(s);
bio->bi_status = write_err ? BLK_STS_IOERR : 0;
bio_endio(bio);
}
@ -1880,7 +1890,7 @@ static void zero_exception(struct dm_snapshot *s, struct dm_exception *e,
dest.sector = bio->bi_iter.bi_sector;
dest.count = s->store->chunk_size;
down(&s->cow_count);
account_start_copy(s);
WARN_ON_ONCE(bio->bi_private);
bio->bi_private = s;
dm_kcopyd_zero(s->kcopyd_client, 1, &dest, 0, zero_callback, bio);