[PATCH 09/10] block: add FALLOC_FL_WRITE_ZEROES support

Zhang Yi
2025-06-04T02:21:56Z

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

Add support for FALLOC_FL_WRITE_ZEROES, if the block device enables the
unmap write zeroes operation, it will issue a write zeroes command.

Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
---
block/fops.c | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/block/fops.c b/block/fops.c
index e1c921549d28..050c16f5974a 100644
--- a/block/fops.c
+++ b/block/fops.c
@@ -841,7 +841,7 @@ 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)
@@ -856,6 +856,13 @@ static long blkdev_fallocate(struct file *file, int mode, loff_t start,
/* Fail if we don't recognize the flags. */
if (mode & ~BLKDEV_FALLOC_FL_SUPPORTED)
return -EOPNOTSUPP;
+ /*
+ * Don't allow writing zeroes if the device does not enable the
+ * unmap write zeroes operation.
+ */
+ if (!bdev_write_zeroes_unmap(bdev) &&
+ (mode & FALLOC_FL_WRITE_ZEROES))
+ return -EOPNOTSUPP;

/* Don't go off the end of the device. */
isize = bdev_nr_bytes(bdev);
@@ -886,6 +893,9 @@ static long blkdev_fallocate(struct file *file, int mode, loff_t start,
case FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE:
flags = BLKDEV_ZERO_NOFALLBACK;
break;
+ case FALLOC_FL_WRITE_ZEROES:
+ flags = 0;
+ break;
default:
error = -EOPNOTSUPP;
goto fail;
--
2.46.1