| Message ID | 20250410030903.3393536-1-weilongping@oppo.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | block: Export __blk_flush_plug to modules | expand |
On Thu, Apr 10, 2025 at 11:09:04AM +0800, LongPing Wei wrote: > Fix the compile error when dm-bufio is built as a module. > > 1. dm-bufio module use blk_flush_plug(); > 2. blk_flush_plug is an inline function and it calls __blk_flush_plug. Then don't call blk_flush_plug from dm-bufio, as drivers should not micro-manage plug flushing. Note that at least in current upstream and linux-next dm-bufio does not actually call blk_flush_plug, so I'm not sure where your report comes from.
On 2025/4/10 15:36, Christoph Hellwig wrote: > On Thu, Apr 10, 2025 at 11:09:04AM +0800, LongPing Wei wrote: >> Fix the compile error when dm-bufio is built as a module. >> >> 1. dm-bufio module use blk_flush_plug(); >> 2. blk_flush_plug is an inline function and it calls __blk_flush_plug. > > Then don't call blk_flush_plug from dm-bufio, as drivers should not > micro-manage plug flushing. > > Note that at least in current upstream and linux-next dm-bufio does > not actually call blk_flush_plug, so I'm not sure where your > report comes from. > Hi, Christoph Stephen reported that a compile error happened when he tried merging device-mapper tree. > Hi all, > > After merging the device-mapper tree, today's linux-next build (powerpc > ppc64_defconfig) failed like this: > > ERROR: modpost: "__blk_flush_plug" [drivers/md/dm-bufio.ko] undefined! > > Caused by commit > > 713ff5c782f5 ("dm-bufio: improve the performance of __dm_bufio_prefetch") > > I have used the device-mapper tree from next-20250409 for today. More details are here. https://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm.git/commit/?h=for-next&id=713ff5c782f5a497bd0e93ca19607daf5bf34005 https://lore.kernel.org/dm-devel/66bf8a8e-0a7d-47b8-9676-dc2e8c596bdb@oppo.com/T/#t Thanks LongPing
Hi, 在 2025/04/10 16:06, LongPing Wei 写道: > On 2025/4/10 15:36, Christoph Hellwig wrote: >> On Thu, Apr 10, 2025 at 11:09:04AM +0800, LongPing Wei wrote: >>> Fix the compile error when dm-bufio is built as a module. >>> >>> 1. dm-bufio module use blk_flush_plug(); >>> 2. blk_flush_plug is an inline function and it calls __blk_flush_plug. >> >> Then don't call blk_flush_plug from dm-bufio, as drivers should not >> micro-manage plug flushing. >> >> Note that at least in current upstream and linux-next dm-bufio does >> not actually call blk_flush_plug, so I'm not sure where your >> report comes from. >> > Hi, Christoph > > Stephen reported that a compile error happened when he tried merging > device-mapper tree. > >> Hi all, >> >> After merging the device-mapper tree, today's linux-next build (powerpc >> ppc64_defconfig) failed like this: >> >> ERROR: modpost: "__blk_flush_plug" [drivers/md/dm-bufio.ko] undefined! >> >> Caused by commit >> >> 713ff5c782f5 ("dm-bufio: improve the performance of >> __dm_bufio_prefetch") >> >> I have used the device-mapper tree from next-20250409 for today. > > > More details are here. > > https://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm.git/commit/?h=for-next&id=713ff5c782f5a497bd0e93ca19607daf5bf34005 So, this patch has compile problem, I think it should be removed from dm tree. BTW, I don't get it from commit message, why you need to flush plug when bio is not contiguous. Other than bio merge, plug is also benefit from batch submitting: __blk_mq_flush_plug_list q->mq_ops->queue_rqs(&plug->mq_list) Thanks, Kuai > > > https://lore.kernel.org/dm-devel/66bf8a8e-0a7d-47b8-9676-dc2e8c596bdb@oppo.com/T/#t > > > Thanks > > LongPing > > . >
On 2025/4/10 17:11, Yu Kuai wrote: > Hi, > > 在 2025/04/10 16:06, LongPing Wei 写道: >> On 2025/4/10 15:36, Christoph Hellwig wrote: >>> On Thu, Apr 10, 2025 at 11:09:04AM +0800, LongPing Wei wrote: >>>> Fix the compile error when dm-bufio is built as a module. >>>> >>>> 1. dm-bufio module use blk_flush_plug(); >>>> 2. blk_flush_plug is an inline function and it calls __blk_flush_plug. >>> >>> Then don't call blk_flush_plug from dm-bufio, as drivers should not >>> micro-manage plug flushing. >>> >>> Note that at least in current upstream and linux-next dm-bufio does >>> not actually call blk_flush_plug, so I'm not sure where your >>> report comes from. >>> >> Hi, Christoph >> >> Stephen reported that a compile error happened when he tried merging >> device-mapper tree. >> >>> Hi all, >>> >>> After merging the device-mapper tree, today's linux-next build (powerpc >>> ppc64_defconfig) failed like this: >>> >>> ERROR: modpost: "__blk_flush_plug" [drivers/md/dm-bufio.ko] undefined! >>> >>> Caused by commit >>> >>> 713ff5c782f5 ("dm-bufio: improve the performance of >>> __dm_bufio_prefetch") >>> >>> I have used the device-mapper tree from next-20250409 for today. >> >> >> More details are here. >> >> https://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux- >> dm.git/commit/?h=for-next&id=713ff5c782f5a497bd0e93ca19607daf5bf34005 > > So, this patch has compile problem, I think it should be removed from > dm tree. > If __blk_flush_plug cannot be exported, this commit need to be removed at first. > BTW, I don't get it from commit message, why you need to flush plug when > bio is not contiguous. Other than bio merge, plug is also benefit from > batch submitting: > > __blk_mq_flush_plug_list > q->mq_ops->queue_rqs(&plug->mq_list) > > Thanks, > Kuai > >> >> >> https://lore.kernel.org/dm-devel/66bf8a8e-0a7d-47b8-9676- >> dc2e8c596bdb@oppo.com/T/#t >> >> Thanks >> >> LongPing >> >> . >> > Previous discussion is here. https://lore.kernel.org/dm-devel/20250325104942.1170388-1-weilongping@oppo.com/T/#ma327528c69f6fd62e15febb5c94164c8e10c7c0d > It seems that verity_prefetch_io doesn't work efficiently. > dm_bufio_prefetch_with_ioprio > __dm_bufio_prefetch > blk_start_plug > for loop > __bufio_new > submit_io > cond_resched > blk_finish_plug > > If more than one hash blocks need to be prefetched, cond_resched will > be called in each loop and blk_finish_plug will be called at the end. > > The requests for hash blocks may have not been dispatched when the > requests for data blocks have been completed. The change ("dm-bufio: improve the performance of __dm_bufio_prefetch") wants to decrease the probability of waiting hash blocks in verity_end_io. Thanks LongPing
On Thu, 10 Apr 2025, Yu Kuai wrote: > Hi, > > 在 2025/04/10 16:06, LongPing Wei 写道: > > On 2025/4/10 15:36, Christoph Hellwig wrote: > > > On Thu, Apr 10, 2025 at 11:09:04AM +0800, LongPing Wei wrote: > > > > Fix the compile error when dm-bufio is built as a module. > > > > > > > > 1. dm-bufio module use blk_flush_plug(); > > > > 2. blk_flush_plug is an inline function and it calls __blk_flush_plug. > > > > > > Then don't call blk_flush_plug from dm-bufio, as drivers should not > > > micro-manage plug flushing. > > > > > > Note that at least in current upstream and linux-next dm-bufio does > > > not actually call blk_flush_plug, so I'm not sure where your > > > report comes from. > > > > > Hi, Christoph > > > > Stephen reported that a compile error happened when he tried merging > > device-mapper tree. > > > > > Hi all, > > > > > > After merging the device-mapper tree, today's linux-next build (powerpc > > > ppc64_defconfig) failed like this: > > > > > > ERROR: modpost: "__blk_flush_plug" [drivers/md/dm-bufio.ko] undefined! > > > > > > Caused by commit > > > > > > 713ff5c782f5 ("dm-bufio: improve the performance of > > > __dm_bufio_prefetch") > > > > > > I have used the device-mapper tree from next-20250409 for today. > > > > > > More details are here. > > > > https://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm.git/commit/?h=for-next&id=713ff5c782f5a497bd0e93ca19607daf5bf34005 > > So, this patch has compile problem, I think it should be removed from > dm tree. OK, I've just removed it. Mikulas > BTW, I don't get it from commit message, why you need to flush plug when > bio is not contiguous. Other than bio merge, plug is also benefit from > batch submitting: > > __blk_mq_flush_plug_list > q->mq_ops->queue_rqs(&plug->mq_list) > > Thanks, > Kuai > > > > > > > https://lore.kernel.org/dm-devel/66bf8a8e-0a7d-47b8-9676-dc2e8c596bdb@oppo.com/T/#t > > > > Thanks > > > > LongPing > > > > . > > >
diff --git a/block/blk-core.c b/block/blk-core.c index e8cc270a453f..4d72ebeb18f7 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -1230,6 +1230,7 @@ void __blk_flush_plug(struct blk_plug *plug, bool from_schedule) plug->cur_ktime = 0; current->flags &= ~PF_BLOCK_TS; } +EXPORT_SYMBOL(__blk_flush_plug); /** * blk_finish_plug - mark the end of a batch of submitted I/O
Fix the compile error when dm-bufio is built as a module. 1. dm-bufio module use blk_flush_plug(); 2. blk_flush_plug is an inline function and it calls __blk_flush_plug. Signed-off-by: LongPing Wei <weilongping@oppo.com> --- block/blk-core.c | 1 + 1 file changed, 1 insertion(+)