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dm: flag clones created by __send_duplicate_bios 

Formally disallow dm_accept_partial_bio() on clones created by
__send_duplicate_bios() because their len_ptr points to a shared
unsigned int.  __send_duplicate_bios() is only used for flush bios
and other "abnormal" bios (discards, writezeroes, etc). And
dm_accept_partial_bio() already didn't support flush bios.

Also refactor __send_changing_extent_only() to reflect it cannot fail.
As such __send_changing_extent_only() can update the clone_info before
__send_duplicate_bios() is called to fan-out __map_bio() calls.

Reviewed-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This commit is contained in:
Mike Snitzer 2022-02-17 23:40:30 -05:00
parent 300432f58b
commit e6fc9f62ce
2 changed files with 30 additions and 21 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
drivers/md/dm-core.h
View File

@ -215,7 +215,8 @@ struct dm_target_io {
struct dm_io *io;
struct dm_target *ti;
unsigned int *len_ptr;
bool inside_dm_io;
bool inside_dm_io:1;
bool is_duplicate_bio:1;
sector_t old_sector;
struct bio clone;
};

48
drivers/md/dm.c
View File

@ -586,6 +586,7 @@ static struct bio *alloc_tio(struct clone_info *ci, struct dm_target *ti,
tio->io = ci->io;
tio->ti = ti;
tio->target_bio_nr = target_bio_nr;
tio->is_duplicate_bio = false;
tio->len_ptr = len;
tio->old_sector = 0;
@ -1087,7 +1088,8 @@ static int dm_dax_zero_page_range(struct dax_device *dax_dev, pgoff_t pgoff,
/*
* A target may call dm_accept_partial_bio only from the map routine. It is
* allowed for all bio types except REQ_PREFLUSH, REQ_OP_ZONE_* zone management
* operations and REQ_OP_ZONE_APPEND (zone append writes).
* operations, REQ_OP_ZONE_APPEND (zone append writes) and any bio serviced by
* __send_duplicate_bios().
*
* dm_accept_partial_bio informs the dm that the target only wants to process
* additional n_sectors sectors of the bio and the rest of the data should be
@ -1118,7 +1120,7 @@ void dm_accept_partial_bio(struct bio *bio, unsigned n_sectors)
struct dm_target_io *tio = clone_to_tio(bio);
unsigned bi_size = bio->bi_iter.bi_size >> SECTOR_SHIFT;
BUG_ON(bio->bi_opf & REQ_PREFLUSH);
BUG_ON(tio->is_duplicate_bio);
BUG_ON(op_is_zone_mgmt(bio_op(bio)));
BUG_ON(bio_op(bio) == REQ_OP_ZONE_APPEND);
BUG_ON(bi_size > *tio->len_ptr);
@ -1246,12 +1248,15 @@ static void __send_duplicate_bios(struct clone_info *ci, struct dm_target *ti,
break;
case 1:
clone = alloc_tio(ci, ti, 0, len, GFP_NOIO);
clone_to_tio(clone)->is_duplicate_bio = true;
__map_bio(clone);
break;
default:
alloc_multiple_bios(&blist, ci, ti, num_bios, len);
while ((clone = bio_list_pop(&blist)))
while ((clone = bio_list_pop(&blist))) {
clone_to_tio(clone)->is_duplicate_bio = true;
__map_bio(clone);
}
break;
}
}
@ -1280,29 +1285,22 @@ static int __send_empty_flush(struct clone_info *ci)
return 0;
}
static int __send_changing_extent_only(struct clone_info *ci, struct dm_target *ti,
unsigned num_bios)
static void __send_changing_extent_only(struct clone_info *ci, struct dm_target *ti,
unsigned num_bios)
{
unsigned len;
/*
* Even though the device advertised support for this type of
* request, that does not mean every target supports it, and
* reconfiguration might also have changed that since the
* check was performed.
*/
if (!num_bios)
return -EOPNOTSUPP;
len = min_t(sector_t, ci->sector_count,
max_io_len_target_boundary(ti, dm_target_offset(ti, ci->sector)));
__send_duplicate_bios(ci, ti, num_bios, &len);
/*
* dm_accept_partial_bio cannot be used with duplicate bios,
* so update clone_info cursor before __send_duplicate_bios().
*/
ci->sector += len;
ci->sector_count -= len;
return 0;
__send_duplicate_bios(ci, ti, num_bios, &len);
}
static bool is_abnormal_io(struct bio *bio)
@ -1324,10 +1322,9 @@ static bool is_abnormal_io(struct bio *bio)
static bool __process_abnormal_io(struct clone_info *ci, struct dm_target *ti,
int *result)
{
struct bio *bio = ci->bio;
unsigned num_bios = 0;
switch (bio_op(bio)) {
switch (bio_op(ci->bio)) {
case REQ_OP_DISCARD:
num_bios = ti->num_discard_bios;
break;
@ -1344,7 +1341,18 @@ static bool __process_abnormal_io(struct clone_info *ci, struct dm_target *ti,
return false;
}
*result = __send_changing_extent_only(ci, ti, num_bios);
/*
* Even though the device advertised support for this type of
* request, that does not mean every target supports it, and
* reconfiguration might also have changed that since the
* check was performed.
*/
if (!num_bios)
*result = -EOPNOTSUPP;
else {
__send_changing_extent_only(ci, ti, num_bios);
*result = 0;
}
return true;
}