On 2020/7/3 0:57, Darrick J. Wong wrote:
On Wed, Jul 01, 2020 at 09:54:01PM -0400, Shijie Luo wrote:
We found a problem when excuting these operations.
$ cd /tmp
$ qemu-img create -f raw test.img 10G
$ mknod -m 0660 /dev/loop0 b 7 0
$ losetup /dev/loop0 test.img
$ mkfs /dev/loop0
Here is the error message.
[ 142.364823] blk_update_request: operation not supported error,
dev loop0, sector 20971392 op 0x9:(WRITE_ZEROES) flags 0x1000800
phys_seg 0 prio class 0
[ 142.371823] blk_update_request: operation not supported error,
dev loop0, sector 5144 op 0x9:(WRITE_ZEROES) flags 0x1000800
phys_seg 0 prio class 0
The problem is that not all filesystem support zero range (eg, tmpfs), if
filesystem doesn 't support zero range, change to punch hole to fix it.
NAK, ZERO_RANGE requires[1] that "Within the specified range, blocks are
preallocated for the regions that span the holes in the file."
PUNCH_HOLE has the opposite effect, and does not qualify as a
replacement.
--D
[1] https://man7.org/linux/man-pages/man2/fallocate.2.html
Thanks for your reply, I know the difference between ZERO_RANGE and
PUNCH_HOLE,
but it's hard to provide ZERO_RANGE operation for all filesystem. Maybe
the formatting
tools should not trigger a NOUNMAP request in this situation.
Fixes: efcfec579f613 ("loop: fix no-unmap write-zeroes request behavior")
Signed-off-by: Shijie Luo <luoshijie1@xxxxxxxxxx>
---
drivers/block/loop.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index c33bbbfd1bd9..504e658adcaf 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -450,6 +450,13 @@ static int lo_fallocate(struct loop_device *lo, struct request *rq, loff_t pos,
}
ret = file->f_op->fallocate(file, mode, pos, blk_rq_bytes(rq));
+
+ if ((ret == -EOPNOTSUPP) && (mode & FALLOC_FL_ZERO_RANGE)) {
+ mode &= ~FALLOC_FL_ZERO_RANGE;
+ mode |= FALLOC_FL_PUNCH_HOLE;
+ ret = file->f_op->fallocate(file, mode, pos, blk_rq_bytes(rq));
+ }
+
if (unlikely(ret && ret != -EINVAL && ret != -EOPNOTSUPP))
ret = -EIO;
out:
--
2.19.1
.
