linux-kernel - [PATCH xfsprogs v2] xfs_io: add FALLOC_FL_WRITE

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Message-Id: <20250813024250.2504126-1-yi.zhang@huaweicloud.com>
Date: Wed, 13 Aug 2025 10:42:50 +0800
From: Zhang Yi <yi.zhang@...weicloud.com>
To: linux-fsdevel@...r.kernel.org,
	linux-block@...r.kernel.org,
	dm-devel@...ts.linux.dev,
	linux-nvme@...ts.infradead.org,
	linux-scsi@...r.kernel.org,
	linux-xfs@...r.kernel.org
Cc: linux-kernel@...r.kernel.org,
	linux-api@...r.kernel.org,
	hch@....de,
	tytso@....edu,
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	yi.zhang@...wei.com,
	yi.zhang@...weicloud.com,
	chengzhihao1@...wei.com,
	yukuai3@...wei.com,
	yangerkun@...wei.com
Subject: [PATCH xfsprogs v2] xfs_io: add FALLOC_FL_WRITE_ZEROES support

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

The Linux kernel (since version 6.17) supports FALLOC_FL_WRITE_ZEROES in
fallocate(2). Add support for FALLOC_FL_WRITE_ZEROES support to the
fallocate utility by introducing a new 'fwzero' command in the xfs_io
tool.

Link: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=278c7d9b5e0c
Signed-off-by: Zhang Yi <yi.zhang@...wei.com>
---
v1->v2:
 - Minor description modification to align with the kernel.

 io/prealloc.c     | 36 ++++++++++++++++++++++++++++++++++++
 man/man8/xfs_io.8 |  6 ++++++
 2 files changed, 42 insertions(+)

diff --git a/io/prealloc.c b/io/prealloc.c
index 8e968c9f..9a64bf53 100644
--- a/io/prealloc.c
+++ b/io/prealloc.c
@@ -30,6 +30,10 @@
 #define FALLOC_FL_UNSHARE_RANGE 0x40
 #endif
 
+#ifndef FALLOC_FL_WRITE_ZEROES
+#define FALLOC_FL_WRITE_ZEROES 0x80
+#endif
+
 static cmdinfo_t allocsp_cmd;
 static cmdinfo_t freesp_cmd;
 static cmdinfo_t resvsp_cmd;
@@ -41,6 +45,7 @@ static cmdinfo_t fcollapse_cmd;
 static cmdinfo_t finsert_cmd;
 static cmdinfo_t fzero_cmd;
 static cmdinfo_t funshare_cmd;
+static cmdinfo_t fwzero_cmd;
 
 static int
 offset_length(
@@ -377,6 +382,27 @@ funshare_f(
 	return 0;
 }
 
+static int
+fwzero_f(
+	int		argc,
+	char		**argv)
+{
+	xfs_flock64_t	segment;
+	int		mode = FALLOC_FL_WRITE_ZEROES;
+
+	if (!offset_length(argv[1], argv[2], &segment)) {
+		exitcode = 1;
+		return 0;
+	}
+
+	if (fallocate(file->fd, mode, segment.l_start, segment.l_len)) {
+		perror("fallocate");
+		exitcode = 1;
+		return 0;
+	}
+	return 0;
+}
+
 void
 prealloc_init(void)
 {
@@ -489,4 +515,14 @@ prealloc_init(void)
 	funshare_cmd.oneline =
 	_("unshares shared blocks within the range");
 	add_command(&funshare_cmd);
+
+	fwzero_cmd.name = "fwzero";
+	fwzero_cmd.cfunc = fwzero_f;
+	fwzero_cmd.argmin = 2;
+	fwzero_cmd.argmax = 2;
+	fwzero_cmd.flags = CMD_NOMAP_OK | CMD_FOREIGN_OK;
+	fwzero_cmd.args = _("off len");
+	fwzero_cmd.oneline =
+	_("zeroes space and eliminates holes by allocating and submitting write zeroes");
+	add_command(&fwzero_cmd);
 }
diff --git a/man/man8/xfs_io.8 b/man/man8/xfs_io.8
index b0dcfdb7..0a673322 100644
--- a/man/man8/xfs_io.8
+++ b/man/man8/xfs_io.8
@@ -550,6 +550,12 @@ With the
 .B -k
 option, use the FALLOC_FL_KEEP_SIZE flag as well.
 .TP
+.BI fwzero " offset length"
+Call fallocate with FALLOC_FL_WRITE_ZEROES flag as described in the
+.BR fallocate (2)
+manual page to allocate and zero blocks within the range by submitting write
+zeroes.
+.TP
 .BI zero " offset length"
 Call xfsctl with
 .B XFS_IOC_ZERO_RANGE
-- 
2.39.2