On Fri, Aug 15, 2025 at 05:59:01PM +0800, Zhang Yi wrote:
> On 2025/8/15 0:54, Darrick J. Wong wrote:
> > On Wed, Aug 13, 2025 at 10:42:50AM +0800, Zhang Yi wrote:
> >> From: Zhang Yi <yi.zh...@huawei.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.zh...@huawei.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;
> >
> > Shouldn't this take a -k to add FALLOC_FL_KEEP_SIZE like fzero?
> >
>
> Since allocating blocks with written extents beyond the inode size
> is not permitted, the FALLOC_FL_WRITE_ZEROES flag cannot be used
> together with the FALLOC_FL_KEEP_SIZE.
Heh, apparently I didn't read the manpage well enough.
Reviewed-by: "Darrick J. Wong" <djw...@kernel.org>
--D
> Thanks,
> Yi.
>
> > (The code otherwise looks fine to me)
> >
> > --D
> >
> >> +
> >> + 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
> >>
> >>
>
>
