| Message ID | 160560849940.336607.1606557482227472957.stgit@localhost.localdomain |
|---|---|
| State | New |
| Series | "loop: fix no-unmap write-zeroes request behavior" |
| Headers | show |
diff --git a/drivers/block/loop.c b/drivers/block/loop.c index 5b124d57b9c0..6308dabc253f 100644 --- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -417,18 +417,20 @@ static int lo_read_transfer(struct loop_device *lo, struct request *rq, return ret; } -static int lo_discard(struct loop_device *lo, struct request *rq, loff_t pos) +static int lo_fallocate(struct loop_device *lo, struct request *rq, loff_t pos, + int mode) { /* - * We use punch hole to reclaim the free space used by the - * image a.k.a. discard. However we do not support discard if - * encryption is enabled, because it may give an attacker - * useful information. + * We use fallocate to manipulate the space mappings used by the image + * a.k.a. discard/zerorange. However we do not support this if + * encryption is enabled, because it may give an attacker useful + * information. */ struct file *file = lo->lo_backing_file; - int mode = FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE; int ret; + mode |= FALLOC_FL_KEEP_SIZE; + if ((!file->f_op->fallocate) || lo->lo_encrypt_key_size) { ret = -EOPNOTSUPP; goto out; @@ -596,9 +598,17 @@ static int do_req_filebacked(struct loop_device *lo, struct request *rq) switch (req_op(rq)) { case REQ_OP_FLUSH: return lo_req_flush(lo, rq); - case REQ_OP_DISCARD: case REQ_OP_WRITE_ZEROES: - return lo_discard(lo, rq, pos); + /* + * If the caller doesn't want deallocation, call zeroout to + * write zeroes the range. Otherwise, punch them out. + */ + return lo_fallocate(lo, rq, pos, + (rq->cmd_flags & REQ_NOUNMAP) ? + FALLOC_FL_ZERO_RANGE : + FALLOC_FL_PUNCH_HOLE); + case REQ_OP_DISCARD: + return lo_fallocate(lo, rq, pos, FALLOC_FL_PUNCH_HOLE); case REQ_OP_WRITE: if (lo->transfer) return lo_write_transfer(lo, rq, pos);
Dropping this as already applied by RedHat: * Thu Apr 16 2020 Frantisek Hrbata <fhrbata@redhat.com> [4.18.0-193.9.el8] - [block] loop: fix no-unmap write-zeroes request behavior (Ming Lei) [1798919] -- Best regards, Konstantin Khorenko, Virtuozzo Linux Kernel Team On 11/17/2020 01:21 PM, Kirill Tkhai wrote: > From: Darrick J. Wong <darrick.wong@oracle.com> > > ms commit efcfec579f61 > > Currently, if the loop device receives a WRITE_ZEROES request, it asks > the underlying filesystem to punch out the range. This behavior is > correct if unmapping is allowed. However, a NOUNMAP request means that > the caller doesn't want us to free the storage backing the range, so > punching out the range is incorrect behavior. > > To satisfy a NOUNMAP | WRITE_ZEROES request, loop should ask the > underlying filesystem to FALLOC_FL_ZERO_RANGE, which is (according to > the fallocate documentation) required to ensure that the entire range is > backed by real storage, which suffices for our purposes. > > Fixes: 19372e2769179dd ("loop: implement REQ_OP_WRITE_ZEROES") > Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com> > Reviewed-by: Christoph Hellwig <hch@lst.de> > Signed-off-by: Jens Axboe <axboe@kernel.dk> > Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com> > --- > drivers/block/loop.c | 26 ++++++++++++++++++-------- > 1 file changed, 18 insertions(+), 8 deletions(-) > > diff --git a/drivers/block/loop.c b/drivers/block/loop.c > index 5b124d57b9c0..6308dabc253f 100644 > --- a/drivers/block/loop.c > +++ b/drivers/block/loop.c > @@ -417,18 +417,20 @@ static int lo_read_transfer(struct loop_device *lo, struct request *rq, > return ret; > } > > -static int lo_discard(struct loop_device *lo, struct request *rq, loff_t pos) > +static int lo_fallocate(struct loop_device *lo, struct request *rq, loff_t pos, > + int mode) > { > /* > - * We use punch hole to reclaim the free space used by the > - * image a.k.a. discard. However we do not support discard if > - * encryption is enabled, because it may give an attacker > - * useful information. > + * We use fallocate to manipulate the space mappings used by the image > + * a.k.a. discard/zerorange. However we do not support this if > + * encryption is enabled, because it may give an attacker useful > + * information. > */ > struct file *file = lo->lo_backing_file; > - int mode = FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE; > int ret; > > + mode |= FALLOC_FL_KEEP_SIZE; > + > if ((!file->f_op->fallocate) || lo->lo_encrypt_key_size) { > ret = -EOPNOTSUPP; > goto out; > @@ -596,9 +598,17 @@ static int do_req_filebacked(struct loop_device *lo, struct request *rq) > switch (req_op(rq)) { > case REQ_OP_FLUSH: > return lo_req_flush(lo, rq); > - case REQ_OP_DISCARD: > case REQ_OP_WRITE_ZEROES: > - return lo_discard(lo, rq, pos); > + /* > + * If the caller doesn't want deallocation, call zeroout to > + * write zeroes the range. Otherwise, punch them out. > + */ > + return lo_fallocate(lo, rq, pos, > + (rq->cmd_flags & REQ_NOUNMAP) ? > + FALLOC_FL_ZERO_RANGE : > + FALLOC_FL_PUNCH_HOLE); > + case REQ_OP_DISCARD: > + return lo_fallocate(lo, rq, pos, FALLOC_FL_PUNCH_HOLE); > case REQ_OP_WRITE: > if (lo->transfer) > return lo_write_transfer(lo, rq, pos); > > > . >