| Message ID | 20160822150720.GA29950@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
At 08/22/2016 11:07 PM, Mike Snitzer wrote: > On Mon, Aug 22 2016 at 4:05am -0400, > Lukas Herbolt <lherbolt@redhat.com> wrote: > >> Hello, >> >> There is patch from Mike. It's part of current pull request to 4.8-rc1 >> For more details check: >> - https://www.redhat.com/archives/dm-devel/2016-July/msg00561.html >> - https://www.redhat.com/archives/dm-devel/2016-August/msg00109.html >> >> Lukas >> >> On Mon, Aug 22, 2016 at 9:31 AM, Qu Wenruo <quwenruo@cn.fujitsu.com> wrote: >>> Hi, Mike and btrfs and dm guys >>> >>> When doing regression test on v4.8-rc1, we found that fstests/btrfs/056 >>> always fails. With the following dmesg: >>> --- >>> Buffer I/O error on dev dm-0, logical block 1310704, async page read >>> Buffer I/O error on dev dm-0, logical block 16, async page read >>> Buffer I/O error on dev dm-0, logical block 16, async page read >>> --- >>> >>> And bisect leads to the following commits: >>> --- >>> commit 99f3c90d0d85708e7401a81ce3314e50bf7f2819 >>> Author: Mike Snitzer <snitzer@redhat.com> >>> Date: Fri Jul 29 13:19:55 2016 -0400 >>> >>> dm flakey: error READ bios during the down_interval >>> --- >>> >>> While according to the document of dm-flakey, it says that when using >>> drop_writes feature, read bios are not affected: >>> --- >>> drop_writes: >>> All write I/O is silently ignored. >>> Read I/O is handled correctly. > > I went back to the dm-flakey.c code at the time that the 'drop_writes' > feature was added via commit b26f5e3d. It does confirm your > understanding of how reads should be handled if drop_writes is enabled. > > Not sure why I thought differently. Please try the following patch. In fact, I quite understand the idea to corrupt READ bio, if drop_writes and corrupt_bio_byte is given at the same time. > > diff --git a/drivers/md/dm-flakey.c b/drivers/md/dm-flakey.c > index 97e446d..6a2e8dd 100644 > --- a/drivers/md/dm-flakey.c > +++ b/drivers/md/dm-flakey.c > @@ -289,15 +289,13 @@ static int flakey_map(struct dm_target *ti, struct bio *bio) > pb->bio_submitted = true; > > /* > - * Map reads as normal only if corrupt_bio_byte set. > + * Error reads if neither corrupt_bio_byte or drop_writes are set. > + * Otherwise, flakey_end_io() will decide if the reads should be modified. > */ > if (bio_data_dir(bio) == READ) { > - /* If flags were specified, only corrupt those that match. */ > - if (fc->corrupt_bio_byte && (fc->corrupt_bio_rw == READ) && > - all_corrupt_bio_flags_match(bio, fc)) > - goto map_bio; > - else > + if (!fc->corrupt_bio_byte && !test_bit(DROP_WRITES, &fc->flags)) > return -EIO; > + goto map_bio; > } > > /* > @@ -334,14 +332,21 @@ static int flakey_end_io(struct dm_target *ti, struct bio *bio, int error) > struct flakey_c *fc = ti->private; > struct per_bio_data *pb = dm_per_bio_data(bio, sizeof(struct per_bio_data)); > > - /* > - * Corrupt successful READs while in down state. > - */ > if (!error && pb->bio_submitted && (bio_data_dir(bio) == READ)) { > - if (fc->corrupt_bio_byte) > + if (fc->corrupt_bio_byte && (fc->corrupt_bio_rw == READ) && > + all_corrupt_bio_flags_match(bio, fc)) { > + /* > + * Corrupt successful matching READs while in down state. > + */ > corrupt_bio_data(bio, fc); > - else > + > + } else if (!test_bit(DROP_WRITES, &fc->flags)) { > + /* > + * Error read during the down_interval if drop_writes > + * wasn't configured. > + */ > return -EIO; > + } > } > > return error; > > It looks good to me, as it can also handle corrupt_bio_byte and drop_writes. Tested-by: Qu Wenruo <quwenruo@cn.fujitsu.com> Thanks, Qu -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/md/dm-flakey.c b/drivers/md/dm-flakey.c index 97e446d..6a2e8dd 100644 --- a/drivers/md/dm-flakey.c +++ b/drivers/md/dm-flakey.c @@ -289,15 +289,13 @@ static int flakey_map(struct dm_target *ti, struct bio *bio) pb->bio_submitted = true; /* - * Map reads as normal only if corrupt_bio_byte set. + * Error reads if neither corrupt_bio_byte or drop_writes are set. + * Otherwise, flakey_end_io() will decide if the reads should be modified. */ if (bio_data_dir(bio) == READ) { - /* If flags were specified, only corrupt those that match. */ - if (fc->corrupt_bio_byte && (fc->corrupt_bio_rw == READ) && - all_corrupt_bio_flags_match(bio, fc)) - goto map_bio; - else + if (!fc->corrupt_bio_byte && !test_bit(DROP_WRITES, &fc->flags)) return -EIO; + goto map_bio; } /* @@ -334,14 +332,21 @@ static int flakey_end_io(struct dm_target *ti, struct bio *bio, int error) struct flakey_c *fc = ti->private; struct per_bio_data *pb = dm_per_bio_data(bio, sizeof(struct per_bio_data)); - /* - * Corrupt successful READs while in down state. - */ if (!error && pb->bio_submitted && (bio_data_dir(bio) == READ)) { - if (fc->corrupt_bio_byte) + if (fc->corrupt_bio_byte && (fc->corrupt_bio_rw == READ) && + all_corrupt_bio_flags_match(bio, fc)) { + /* + * Corrupt successful matching READs while in down state. + */ corrupt_bio_data(bio, fc); - else + + } else if (!test_bit(DROP_WRITES, &fc->flags)) { + /* + * Error read during the down_interval if drop_writes + * wasn't configured. + */ return -EIO; + } } return error;