Hi
Here I'm sending that patch for REQ_NOWAIT for review.
It is not tested, except for some trivial tests that involve logical
volume activation.
I found out that it seems easier to propagate the error using bits in
clone_info rather than changing return codes for each affected function.
Mikulas
Signed-off-by: Mikulas Patocka <mpato...@redhat.com>
---
drivers/md/dm.c | 51 +++++++++++++++++++++++++++++++++++++++++++++------
1 file changed, 45 insertions(+), 6 deletions(-)
Index: linux-2.6/drivers/md/dm.c
===================================================================
--- linux-2.6.orig/drivers/md/dm.c
+++ linux-2.6/drivers/md/dm.c
@@ -87,6 +87,8 @@ struct clone_info {
unsigned int sector_count;
bool is_abnormal_io:1;
bool submit_as_polled:1;
+ bool is_nowait:1;
+ bool nowait_failed:1;
};
static inline struct dm_target_io *clone_to_tio(struct bio *clone)
@@ -570,13 +572,21 @@ static void dm_end_io_acct(struct dm_io
dm_io_acct(io, true);
}
-static struct dm_io *alloc_io(struct mapped_device *md, struct bio *bio)
+static struct dm_io *alloc_io(struct clone_info *ci, struct mapped_device *md,
struct bio *bio)
{
struct dm_io *io;
struct dm_target_io *tio;
struct bio *clone;
- clone = bio_alloc_clone(NULL, bio, GFP_NOIO, &md->mempools->io_bs);
+ if (unlikely(ci->is_nowait)) {
+ clone = bio_alloc_clone(NULL, bio, GFP_NOWAIT,
&md->mempools->io_bs);
+ if (!clone) {
+ ci->nowait_failed = true;
+ return NULL;
+ }
+ } else {
+ clone = bio_alloc_clone(NULL, bio, GFP_NOIO,
&md->mempools->io_bs);
+ }
tio = clone_to_tio(clone);
tio->flags = 0;
dm_tio_set_flag(tio, DM_TIO_INSIDE_DM_IO);
@@ -1503,6 +1513,11 @@ static void alloc_multiple_bios(struct b
while ((bio = bio_list_pop(blist)))
free_tio(bio);
+
+ if (ci->is_nowait) {
+ ci->nowait_failed = true;
+ return;
+ }
}
}
@@ -1519,7 +1534,15 @@ static unsigned int __send_duplicate_bio
case 1:
if (len)
setup_split_accounting(ci, *len);
- clone = alloc_tio(ci, ti, 0, len, GFP_NOIO);
+ if (unlikely(ci->is_nowait)) {
+ clone = alloc_tio(ci, ti, 0, len, GFP_NOWAIT);
+ if (!clone) {
+ ci->nowait_failed = true;
+ return 0;
+ }
+ } else {
+ clone = alloc_tio(ci, ti, 0, len, GFP_NOIO);
+ }
__map_bio(clone);
ret = 1;
break;
@@ -1656,7 +1679,7 @@ static blk_status_t __process_abnormal_i
__send_changing_extent_only(ci, ti, num_bios,
max_granularity, max_sectors);
- return BLK_STS_OK;
+ return likely(!ci->nowait_failed) ? BLK_STS_OK : BLK_STS_AGAIN;
}
/*
@@ -1729,7 +1752,15 @@ static blk_status_t __split_and_process_
len = min_t(sector_t, max_io_len(ti, ci->sector), ci->sector_count);
setup_split_accounting(ci, len);
- clone = alloc_tio(ci, ti, 0, &len, GFP_NOIO);
+ if (unlikely(ci->is_nowait)) {
+ clone = alloc_tio(ci, ti, 0, &len, GFP_NOWAIT);
+ if (unlikely(!clone)) {
+ ci->nowait_failed = true;
+ return BLK_STS_AGAIN;
+ }
+ } else {
+ clone = alloc_tio(ci, ti, 0, &len, GFP_NOIO);
+ }
__map_bio(clone);
ci->sector += len;
@@ -1741,8 +1772,10 @@ static blk_status_t __split_and_process_
static void init_clone_info(struct clone_info *ci, struct mapped_device *md,
struct dm_table *map, struct bio *bio, bool
is_abnormal)
{
+ ci->is_nowait = !!(bio->bi_opf & REQ_NOWAIT);
+ ci->nowait_failed = false;
ci->map = map;
- ci->io = alloc_io(md, bio);
+ ci->io = alloc_io(ci, md, bio);
ci->bio = bio;
ci->is_abnormal_io = is_abnormal;
ci->submit_as_polled = false;
@@ -1778,10 +1811,16 @@ static void dm_split_and_process_bio(str
}
init_clone_info(&ci, md, map, bio, is_abnormal);
+ if (unlikely(ci.nowait_failed)) {
+ error = BLK_STS_AGAIN;
+ goto out;
+ }
io = ci.io;
if (bio->bi_opf & REQ_PREFLUSH) {
__send_empty_flush(&ci);
+ if (unlikely(ci.nowait_failed))
+ error = BLK_STS_AGAIN;
/* dm_io_complete submits any data associated with flush */
goto out;
}
--
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