On Mon, Nov 04 2013 at 12:49pm -0500, Mikulas Patocka <mpatocka@xxxxxxxxxx> wrote: > > > On Mon, 4 Nov 2013, Mike Snitzer wrote: > > > On Mon, Nov 04 2013 at 10:25am -0500, > > Mikulas Patocka <mpatocka@xxxxxxxxxx> wrote: > > > > > > > > > > > On Mon, 4 Nov 2013, Mike Snitzer wrote: > > > > > > > On Mon, Nov 04 2013 at 10:06am -0500, > > > > Mikulas Patocka <mpatocka@xxxxxxxxxx> wrote: > > > > > > > > > > The code uses atomic_inc for restoration of bi_remaining. This patch > > > > > changes it to atomic_set(1) to avoid an interlocked instruction. In the > > > > > target's bi_endio routine we are sure that bi_remaining is zero > > > > > (otherwise, the bi_endio routine wouldn't be called) and there are no > > > > > concurrent users of the bio, so we can replace atomic_inc with > > > > > atomic_set(1). > > > > > > > > This isn't DM-specific. Shouldn't the other places in the tree that use > > > > atomic_inc on bi_remaining should really be converted at the same time? > > > > > > There is no 'atomic_inc.*bi_remaining' in other drivers. > > > > Wrong. I know btrfs has at least one. As does bcache afaik. > > grep -r 'atomic_inc.*bi_remaining' * yilds no hits in btrfs or bcache (on > git://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux-block.git , > branch remotes/origin/for-next). It only finds > drivers/md/dm-cache-target.c, drivers/md/dm-verity.c, > drivers/md/dm-snap.c, drivers/md/dm-thin.c. Maybe in other git trees there > are more cases of this. Here is the btrfs one I was thinking of from Chris: https://patchwork.kernel.org/patch/3123121/ Should probably make its way into linux-block.git, Jens? -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
