lkml.org 
[lkml]   [2014]   [Nov]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [dm-devel] dm-bufio: fix memleak when using a dm_buffer's inline bio
    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@oracle.com> 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@oracle.com>
    >
    > 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.

    --D

    >
    > --
    > dm-devel mailing list
    > dm-devel@redhat.com
    > https://www.redhat.com/mailman/listinfo/dm-devel


    \
     
     \ /
      Last update: 2014-11-26 05:41    [W:3.301 / U:0.044 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site