On Fri, Aug 15, 2025 at 05:29:19PM +0800, Zhang Yi wrote:

Thank you for your review comments!

On 2025/8/15 0:52, Darrick J. Wong wrote:

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On Wed, Aug 13, 2025 at 10:40:15AM +0800, Zhang Yi wrote:

quoted

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

The Linux kernel (since version 6.17) supports FALLOC_FL_WRITE_ZEROES in
fallocate(2). Add support for FALLOC_FL_WRITE_ZEROES to the fallocate
utility by introducing a new option -w|--write-zeroes.

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

 sys-utils/fallocate.1.adoc | 11 +++++++++--
 sys-utils/fallocate.c      | 20 ++++++++++++++++----
 2 files changed, 25 insertions(+), 6 deletions(-)

diff --git a/sys-utils/fallocate.1.adoc b/sys-utils/fallocate.1.adoc
index 44ee0ef4c..0ec9ff9a9 100644
--- a/sys-utils/fallocate.1.adoc
+++ b/sys-utils/fallocate.1.adoc

@@ -12,7 +12,7 @@ fallocate - preallocate or deallocate space to a file

<snip all the long lines>

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+*-w*, *--write-zeroes*::
+Zeroes space in the byte range starting at _offset_ and continuing
for _length_ bytes. Within the specified range, blocks are
preallocated for the regions that span the holes in the file. After a
successful call, subsequent reads from this range will return zeroes,
subsequent writes to that range do not require further changes to the
file mapping metadata.

"...will return zeroes and subsequent writes to that range..." ?

Yeah.

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++
+Zeroing is done within the filesystem by preferably submitting write

I think we should say less about what the filesystem actually does to
preserve some flexibility:

"Zeroing is done within the filesystem. The filesystem may use a
hardware accelerated zeroing command, or it may submit regular writes.
The behavior depends on the filesystem design and available hardware."

Sure.

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zeores commands, the alternative way is submitting actual zeroed data,
the specified range will be converted into written extents. The write
zeroes command is typically faster than write actual data if the
device supports unmap write zeroes, the specified range will not be
physically zeroed out on the device.
++
+Options *--keep-size* can not be specified for the write-zeroes
operation.
+
 include::man-common/help-version.adoc[]
 
 == AUTHORS

[..]

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@@ -429,6 +438,9 @@ int main(int argc, char **argv)
 			else if (mode & FALLOC_FL_ZERO_RANGE)
 				fprintf(stdout, _("%s: %s (%ju bytes) zeroed.\n"),
 								filename, str, length);
+			else if (mode & FALLOC_FL_WRITE_ZEROES)
+				fprintf(stdout, _("%s: %s (%ju bytes) write zeroed.\n"),

"write zeroed" is a little strange, but I don't have a better
suggestion. :)

Hmm... What about simply using "zeroed", the same to FALLOC_FL_ZERO_RANGE?
Users should be aware of the parameters they have passed to fallocate(),
so they should not use this print for further differentiation.

No thanks, different inputs should produce different outputs. :)

--D

Thanks,
Yi.