On Wed, Nov 26, 2014 at 09:28:32AM -0500, Mike Snitzer wrote: > On Tue, Nov 25 2014 at 11:00pm -0500, > Darrick J. Wong <darrick.wong@xxxxxxxxxx> wrote: > > > On Tue, Nov 25, 2014 at 10:41:04PM -0500, Mike Snitzer wrote: > > > On Tue, Nov 25 2014 at 8:45pm -0500, > > > Darrick J. Wong <darrick.wong@xxxxxxxxxx> wrote: > > > > > > > When dm-bufio sets out to use the bio built into a struct dm_buffer to > > > > issue an IO, it needs to call bio_reset after it's done with the bio > > > > so that we can free things attached to the bio such as the integrity > > > > payload. Therefore, inject our own endio callback to take care of > > > > the bio_reset after calling submit_io's end_io callback. > > > > > > > > Test case: > > > > 1. modprobe scsi_debug delay=0 dif=1 dix=199 ato=1 dev_size_mb=300 > > > > 2. Set up a dm-bufio client, e.g. dm-verity, on the scsi_debug device > > > > 3. Repeatedly read metadata and watch kmalloc-192 leak! > > > > > > > > Fix is against 3.18-rc6. > > > > > > > > Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx> > > > > > > Thanks for reporting/fixing this. > > > > > > Alternatively I think we could just call bio_reset() in submit_io(), > > > e.g.: > > > > > > diff --git a/drivers/md/dm-bufio.c b/drivers/md/dm-bufio.c > > > index afe7971..e7036e3 100644 > > > --- a/drivers/md/dm-bufio.c > > > +++ b/drivers/md/dm-bufio.c > > > @@ -579,6 +579,8 @@ static void submit_io(struct dm_buffer *b, int rw, sector_t block, > > > if (rw == WRITE && b->c->write_callback) > > > b->c->write_callback(b); > > > > > > + bio_reset(&b->bio); > > > + > > > if (b->c->block_size <= DM_BUFIO_INLINE_VECS * PAGE_SIZE && > > > b->data_mode != DATA_MODE_VMALLOC) > > > use_inline_bio(b, rw, block, end_io); > > > > > > What do you think? > > > > I decided to call bio_reset after calling end_io so that we can free > > the integrity buffer as soon as we're done with the bio. Calling > > bio_reset just prior to the next submit_bio as this snippet does means > > that the integrity buffer remains attached to the bio until just > > before the next submit_bio call, which could be a while. > > > > Also, I think use_dmio results in a new bio being used instead of the > > bio embedded in the dm_buffer, so it shouldn't be necessary to reset > > the bio if the previous IO had use_dmio'd. > > OK, yeah, a new embedded bio is created as a side-effect of allocating a > new dm_buffer. So we have to use bi_end_io like you've done. > > I didn't like seeing your use of .bi_private (because in the context of > bios that are passed into DM: .bi_private must always be preserved so as > not to break upper layers of the IO stack that might be using it). <nod> I hadn't considered that not restoring .bi_private without comment would raise eyebrows in a space where the norm is that they must always be preserved. :) > But in the context of bufio's embedded bio, using .bi_private seems > fine. Just needs a comment. I'll fixup and get your patch staged (and > will CC stable). The staged patch looks good, thank you! --D > > Thanks again, > Mike > > -- > dm-devel mailing list > dm-devel@xxxxxxxxxx > https://www.redhat.com/mailman/listinfo/dm-devel -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
