linux-kernel - [PATCH 09/10] block: add FALLOC_FL_WRITE

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Message-ID: <20250604020850.1304633-10-yi.zhang@huaweicloud.com>
Date: Wed,  4 Jun 2025 10:08:49 +0800
From: Zhang Yi <yi.zhang@...weicloud.com>
To: linux-fsdevel@...r.kernel.org,
	linux-ext4@...r.kernel.org,
	linux-block@...r.kernel.org,
	dm-devel@...ts.linux.dev,
	linux-nvme@...ts.infradead.org,
	linux-scsi@...r.kernel.org
Cc: linux-xfs@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	hch@....de,
	tytso@....edu,
	djwong@...nel.org,
	john.g.garry@...cle.com,
	bmarzins@...hat.com,
	chaitanyak@...dia.com,
	shinichiro.kawasaki@....com,
	brauner@...nel.org,
	martin.petersen@...cle.com,
	yi.zhang@...wei.com,
	yi.zhang@...weicloud.com,
	chengzhihao1@...wei.com,
	yukuai3@...wei.com,
	yangerkun@...wei.com
Subject: [PATCH 09/10] block: add FALLOC_FL_WRITE_ZEROES support

From: Zhang Yi <yi.zhang@...wei.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@...wei.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