Re: [PATCH] f2fs: allocate a bio for discarding when actually issuing it

From: Jaegeuk Kim
Date: Wed Mar 08 2017 - 16:52:33 EST

On 03/08, Christoph Hellwig wrote:
> On Tue, Mar 07, 2017 at 06:33:33PM -0800, Jaegeuk Kim wrote:
> > Let's allocate a bio when issuing discard commands later.
>
> Does this solve the issue with your queue stalls?

No, the patch just changes bio_alloc timings, but the stall happens when doing
submit_bio.

Thanks,

>
> >
> > Signed-off-by: Jaegeuk Kim <jaegeuk@xxxxxxxxxx>
> > ---
> > fs/f2fs/f2fs.h | 4 +-
> > fs/f2fs/segment.c | 113 ++++++++++++++++++++++++++++--------------------------
> > 2 files changed, 62 insertions(+), 55 deletions(-)
> >
> > diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> > index a58c2e43bd2a..870bb4d9bc65 100644
> > --- a/fs/f2fs/f2fs.h
> > +++ b/fs/f2fs/f2fs.h
> > @@ -197,10 +197,12 @@ enum {
> > struct discard_cmd {
> > struct list_head list; /* command list */
> > struct completion wait; /* compleation */
> > + struct block_device *bdev; /* bdev */
> > block_t lstart; /* logical start address */
> > + block_t start; /* actual start address in dev */
> > block_t len; /* length */
> > - struct bio *bio; /* bio */
> > int state; /* state */
> > + int error; /* bio error */
> > };
> >
> > struct discard_cmd_control {
> > diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> > index 50c65cc4645a..d8f9e6c895cd 100644
> > --- a/fs/f2fs/segment.c
> > +++ b/fs/f2fs/segment.c
> > @@ -636,7 +636,8 @@ static void locate_dirty_segment(struct f2fs_sb_info *sbi, unsigned int segno)
> > }
> >
> > static void __add_discard_cmd(struct f2fs_sb_info *sbi,
> > - struct bio *bio, block_t lstart, block_t len)
> > + struct block_device *bdev, block_t lstart,
> > + block_t start, block_t len)
> > {
> > struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
> > struct list_head *cmd_list = &(dcc->discard_cmd_list);
> > @@ -644,9 +645,9 @@ static void __add_discard_cmd(struct f2fs_sb_info *sbi,
> >
> > dc = f2fs_kmem_cache_alloc(discard_cmd_slab, GFP_NOFS);
> > INIT_LIST_HEAD(&dc->list);
> > - dc->bio = bio;
> > - bio->bi_private = dc;
> > + dc->bdev = bdev;
> > dc->lstart = lstart;
> > + dc->start = start;
> > dc->len = len;
> > dc->state = D_PREP;
> > init_completion(&dc->wait);
> > @@ -658,22 +659,66 @@ static void __add_discard_cmd(struct f2fs_sb_info *sbi,
> >
> > static void __remove_discard_cmd(struct f2fs_sb_info *sbi, struct discard_cmd *dc)
> > {
> > - int err = dc->bio->bi_error;
> > -
> > if (dc->state == D_DONE)
> > atomic_dec(&(SM_I(sbi)->dcc_info->submit_discard));
> >
> > - if (err == -EOPNOTSUPP)
> > - err = 0;
> > + if (dc->error == -EOPNOTSUPP)
> > + dc->error = 0;
> >
> > - if (err)
> > + if (dc->error)
> > f2fs_msg(sbi->sb, KERN_INFO,
> > - "Issue discard failed, ret: %d", err);
> > - bio_put(dc->bio);
> > + "Issue discard failed, ret: %d", dc->error);
> > list_del(&dc->list);
> > kmem_cache_free(discard_cmd_slab, dc);
> > }
> >
> > +static void f2fs_submit_discard_endio(struct bio *bio)
> > +{
> > + struct discard_cmd *dc = (struct discard_cmd *)bio->bi_private;
> > +
> > + complete(&dc->wait);
> > + dc->error = bio->bi_error;
> > + dc->state = D_DONE;
> > + bio_put(bio);
> > +}
> > +
> > +/* this function is copied from blkdev_issue_discard from block/blk-lib.c */
> > +static int __submit_discard_cmd(struct discard_cmd *dc)
> > +{
> > + struct bio *bio = NULL;
> > + int err;
> > +
> > + err = __blkdev_issue_discard(dc->bdev,
> > + SECTOR_FROM_BLOCK(dc->start),
> > + SECTOR_FROM_BLOCK(dc->len),
> > + GFP_NOFS, 0, &bio);
> > + if (!err && bio) {
> > + bio->bi_private = dc;
> > + bio->bi_end_io = f2fs_submit_discard_endio;
> > + bio->bi_opf |= REQ_SYNC;
> > + submit_bio(bio);
> > + }
> > + dc->state = D_SUBMIT;
> > + return err;
> > +}
> > +
> > +static int __queue_discard_cmd(struct f2fs_sb_info *sbi,
> > + struct block_device *bdev, block_t blkstart, block_t blklen)
> > +{
> > + block_t lblkstart = blkstart;
> > +
> > + trace_f2fs_issue_discard(bdev, blkstart, blklen);
> > +
> > + if (sbi->s_ndevs) {
> > + int devi = f2fs_target_device_index(sbi, blkstart);
> > +
> > + blkstart -= FDEV(devi).start_blk;
> > + }
> > + __add_discard_cmd(sbi, bdev, lblkstart, blkstart, blklen);
> > + wake_up(&SM_I(sbi)->dcc_info->discard_wait_queue);
> > + return 0;
> > +}
> > +
> > /* This should be covered by global mutex, &sit_i->sentry_lock */
> > void f2fs_wait_discard_bio(struct f2fs_sb_info *sbi, block_t blkaddr)
> > {
> > @@ -690,8 +735,7 @@ void f2fs_wait_discard_bio(struct f2fs_sb_info *sbi, block_t blkaddr)
> >
> > if (blkaddr == NULL_ADDR) {
> > if (dc->state == D_PREP) {
> > - dc->state = D_SUBMIT;
> > - submit_bio(dc->bio);
> > + __submit_discard_cmd(dc);
> > atomic_inc(&dcc->submit_discard);
> > }
> > continue;
> > @@ -716,14 +760,6 @@ void f2fs_wait_discard_bio(struct f2fs_sb_info *sbi, block_t blkaddr)
> > mutex_unlock(&dcc->cmd_lock);
> > }
> >
> > -static void f2fs_submit_discard_endio(struct bio *bio)
> > -{
> > - struct discard_cmd *dc = (struct discard_cmd *)bio->bi_private;
> > -
> > - complete(&dc->wait);
> > - dc->state = D_DONE;
> > -}
> > -
> > static int issue_discard_thread(void *data)
> > {
> > struct f2fs_sb_info *sbi = data;
> > @@ -742,8 +778,7 @@ static int issue_discard_thread(void *data)
> > mutex_lock(&dcc->cmd_lock);
> > list_for_each_entry_safe(dc, tmp, cmd_list, list) {
> > if (dc->state == D_PREP) {
> > - dc->state = D_SUBMIT;
> > - submit_bio(dc->bio);
> > + __submit_discard_cmd(dc);
> > atomic_inc(&dcc->submit_discard);
> > if (iter++ > DISCARD_ISSUE_RATE)
> > break;
> > @@ -763,36 +798,6 @@ static int issue_discard_thread(void *data)
> > goto repeat;
> > }
> >
> > -
> > -/* this function is copied from blkdev_issue_discard from block/blk-lib.c */
> > -static int __f2fs_issue_discard_async(struct f2fs_sb_info *sbi,
> > - struct block_device *bdev, block_t blkstart, block_t blklen)
> > -{
> > - struct bio *bio = NULL;
> > - block_t lblkstart = blkstart;
> > - int err;
> > -
> > - trace_f2fs_issue_discard(bdev, blkstart, blklen);
> > -
> > - if (sbi->s_ndevs) {
> > - int devi = f2fs_target_device_index(sbi, blkstart);
> > -
> > - blkstart -= FDEV(devi).start_blk;
> > - }
> > - err = __blkdev_issue_discard(bdev,
> > - SECTOR_FROM_BLOCK(blkstart),
> > - SECTOR_FROM_BLOCK(blklen),
> > - GFP_NOFS, 0, &bio);
> > - if (!err && bio) {
> > - bio->bi_end_io = f2fs_submit_discard_endio;
> > - bio->bi_opf |= REQ_SYNC;
> > -
> > - __add_discard_cmd(sbi, bio, lblkstart, blklen);
> > - wake_up(&SM_I(sbi)->dcc_info->discard_wait_queue);
> > - }
> > - return err;
> > -}
> > -
> > #ifdef CONFIG_BLK_DEV_ZONED
> > static int __f2fs_issue_discard_zone(struct f2fs_sb_info *sbi,
> > struct block_device *bdev, block_t blkstart, block_t blklen)
> > @@ -816,7 +821,7 @@ static int __f2fs_issue_discard_zone(struct f2fs_sb_info *sbi,
> > case BLK_ZONE_TYPE_CONVENTIONAL:
> > if (!blk_queue_discard(bdev_get_queue(bdev)))
> > return 0;
> > - return __f2fs_issue_discard_async(sbi, bdev, lblkstart, blklen);
> > + return __queue_discard_cmd(sbi, bdev, lblkstart, blklen);
> > case BLK_ZONE_TYPE_SEQWRITE_REQ:
> > case BLK_ZONE_TYPE_SEQWRITE_PREF:
> > sector = SECTOR_FROM_BLOCK(blkstart);
> > @@ -848,7 +853,7 @@ static int __issue_discard_async(struct f2fs_sb_info *sbi,
> > bdev_zoned_model(bdev) != BLK_ZONED_NONE)
> > return __f2fs_issue_discard_zone(sbi, bdev, blkstart, blklen);
> > #endif
> > - return __f2fs_issue_discard_async(sbi, bdev, blkstart, blklen);
> > + return __queue_discard_cmd(sbi, bdev, blkstart, blklen);
> > }
> >
> > static int f2fs_issue_discard(struct f2fs_sb_info *sbi,
> > --
> > 2.11.0
> >
> ---end quoted text---