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authorDarrick J. Wong <darrick.wong@oracle.com>2019-10-30 20:29:48 -0700
committerJens Axboe <axboe@kernel.dk>2019-11-01 08:43:20 -0600
commitefcfec579f6139528c9e6925eca2bc4a36da65c6 (patch)
treefcb52fe28df557856d7d4f78204d8952f85a9693 /drivers/block
parenta4414aedf4bc923c1faa24d72d14f14c2b93e48f (diff)
loop: fix no-unmap write-zeroes request behavior
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>
Diffstat (limited to 'drivers/block')
-rw-r--r--drivers/block/loop.c26
1 files changed, 18 insertions, 8 deletions
diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index f6f77eaa7217..ef6e251857c8 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -417,18 +417,20 @@ out_free_page:
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);