Gentle ping. On 2019/6/5 21:27, zhangyi (F) Wrote: > Currently, although we submit super bios in log-write thread orderly > (the super.nr_entries is incremented by each logged entry), the > submit_bio() cannot make sure that each super sector is written to log > device in order. So the submitting bio of each super sector may be > out-of-order, and then the final nr_entries maybe small than the real > entries submitted. > > This problem can be reproduced by the xfstests generic/455 with ext4, > which may complained below after running the test: > > QA output created by 455 > -Silence is golden > +mark 'end' does not exist > > This patch serialize submitting super secotrs to make sure each super > sectors are written to log disk in order, so that we can prevent the > latest nr_entries be rewritten by some old super bios. > > Signed-off-by: zhangyi (F) <[email protected]> > Suggested-by: Josef Bacik <[email protected]> > --- > Changes since v1: > - Switch to use completion instead of wait_queue to synchronize > submitting super bios. > > drivers/md/dm-log-writes.c | 25 +++++++++++++++++++++++-- > 1 file changed, 23 insertions(+), 2 deletions(-) > > diff --git a/drivers/md/dm-log-writes.c b/drivers/md/dm-log-writes.c > index 9ea2b02..4854246 100644 > --- a/drivers/md/dm-log-writes.c > +++ b/drivers/md/dm-log-writes.c > @@ -60,6 +60,7 @@ > > #define WRITE_LOG_VERSION 1ULL > #define WRITE_LOG_MAGIC 0x6a736677736872ULL > +#define WRITE_LOG_SUPER_SECTOR 0 > > /* > * The disk format for this is braindead simple. > @@ -115,6 +116,7 @@ struct log_writes_c { > struct list_head logging_blocks; > wait_queue_head_t wait; > struct task_struct *log_kthread; > + struct completion super_done; > }; > > struct pending_block { > @@ -180,6 +182,15 @@ static void log_end_io(struct bio *bio) > bio_put(bio); > } > > +static void log_end_super(struct bio *bio) > +{ > + struct log_writes_c *lc = bio->bi_private; > + > + /* Wake up log-write kthread that super has been written */ > + complete(&lc->super_done); > + log_end_io(bio); > +} > + > /* > * Meant to be called if there is an error, it will free all the pages > * associated with the block. > @@ -215,7 +226,8 @@ static int write_metadata(struct log_writes_c *lc, void > *entry, > bio->bi_iter.bi_size = 0; > bio->bi_iter.bi_sector = sector; > bio_set_dev(bio, lc->logdev->bdev); > - bio->bi_end_io = log_end_io; > + bio->bi_end_io = (sector == WRITE_LOG_SUPER_SECTOR) ? > + log_end_super : log_end_io; > bio->bi_private = lc; > bio_set_op_attrs(bio, REQ_OP_WRITE, 0); > > @@ -418,11 +430,19 @@ static int log_super(struct log_writes_c *lc) > super.nr_entries = cpu_to_le64(lc->logged_entries); > super.sectorsize = cpu_to_le32(lc->sectorsize); > > - if (write_metadata(lc, &super, sizeof(super), NULL, 0, 0)) { > + if (write_metadata(lc, &super, sizeof(super), NULL, 0, > + WRITE_LOG_SUPER_SECTOR)) { > DMERR("Couldn't write super"); > return -1; > } > > + /* > + * Super sector should be writen in-order, or else the > + * nr_entries could be rewritten by the old bio and small > + * than the real submitted entries. > + */ > + wait_for_completion_io(&lc->super_done); > + > return 0; > } > > @@ -531,6 +551,7 @@ static int log_writes_ctr(struct dm_target *ti, unsigned > int argc, char **argv) > INIT_LIST_HEAD(&lc->unflushed_blocks); > INIT_LIST_HEAD(&lc->logging_blocks); > init_waitqueue_head(&lc->wait); > + init_completion(&lc->super_done); > atomic_set(&lc->io_blocks, 0); > atomic_set(&lc->pending_blocks, 0); > >
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