[RFC PATCH -next v3 08/10] block: add FALLOC_FL_WRITE_ZEROES support

Zhang Yi
2025-03-18T07:44:17Z

From: Zhang Yi <yi.zhang@huawei.com>

Add support for FALLOC_FL_WRITE_ZEROES. It directly calls
blkdev_issue_zeroout() with flags set to 0. The underlying process will
attempt to use the fastest method for issuing zeroes. First, the block
layer will try to issue a write zeroes command if the storage device
supports it; if not, it will fall back to issuing zeroed data. Then, the
storage device driver may attempt to submit an unmap write zero command
if the device supports it; if not, the driver may fall back to
submitting a no-unmap write zeroes command.

Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
---
block/fops.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/block/fops.c b/block/fops.c
index be9f1dbea9ce..5a519581d7e3 100644
--- a/block/fops.c
+++ b/block/fops.c
@@ -803,7 +803,7 @@ static ssize_t blkdev_read_iter(struct kiocb *iocb, struct iov_iter *to)

#define BLKDEV_FALLOC_FL_SUPPORTED \
(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE | \
- FALLOC_FL_ZERO_RANGE)
+ FALLOC_FL_ZERO_RANGE | FALLOC_FL_WRITE_ZEROES)

static long blkdev_fallocate(struct file *file, int mode, loff_t start,
loff_t len)
@@ -862,6 +862,15 @@ static long blkdev_fallocate(struct file *file, int mode, loff_t start,
len >> SECTOR_SHIFT, GFP_KERNEL,
BLKDEV_ZERO_NOFALLBACK);
break;
+ case FALLOC_FL_WRITE_ZEROES:
+ error = truncate_bdev_range(bdev, file_to_blk_mode(file), start, end);
+ if (error)
+ goto fail;
+
+ error = blkdev_issue_zeroout(bdev, start >> SECTOR_SHIFT,
+ len >> SECTOR_SHIFT, GFP_KERNEL,
+ 0);
+ break;
default:
error = -EOPNOTSUPP;
}
--
2.46.1