On Wed, Aug 13, 2025 at 10:40:15AM +0800, Zhang Yi wrote: > From: Zhang Yi <yi.zhang@xxxxxxxxxx> > > 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@xxxxxxxxxx> > --- > 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> > +*-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..." ? > ++ > +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." > 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 > diff --git a/sys-utils/fallocate.c b/sys-utils/fallocate.c > index 13bf52915..8d37fdad7 100644 > --- a/sys-utils/fallocate.c > +++ b/sys-utils/fallocate.c > @@ -40,7 +40,7 @@ > #if defined(HAVE_LINUX_FALLOC_H) && \ > (!defined(FALLOC_FL_KEEP_SIZE) || !defined(FALLOC_FL_PUNCH_HOLE) || \ > !defined(FALLOC_FL_COLLAPSE_RANGE) || !defined(FALLOC_FL_ZERO_RANGE) || \ > - !defined(FALLOC_FL_INSERT_RANGE)) > + !defined(FALLOC_FL_INSERT_RANGE) || !defined(FALLOC_FL_WRITE_ZEROES)) > # include <linux/falloc.h> /* non-libc fallback for FALLOC_FL_* flags */ > #endif > > @@ -65,6 +65,10 @@ > # define FALLOC_FL_INSERT_RANGE 0x20 > #endif > > +#ifndef FALLOC_FL_WRITE_ZEROES > +# define FALLOC_FL_WRITE_ZEROES 0x80 > +#endif > + > #include "nls.h" > #include "strutils.h" > #include "c.h" > @@ -94,6 +98,7 @@ static void __attribute__((__noreturn__)) usage(void) > fputs(_(" -o, --offset <num> offset for range operations, in bytes\n"), out); > fputs(_(" -p, --punch-hole replace a range with a hole (implies -n)\n"), out); > fputs(_(" -z, --zero-range zero and ensure allocation of a range\n"), out); > + fputs(_(" -w, --write-zeroes write zeroes and ensure allocation of a range\n"), out); > #ifdef HAVE_POSIX_FALLOCATE > fputs(_(" -x, --posix use posix_fallocate(3) instead of fallocate(2)\n"), out); > #endif > @@ -304,6 +309,7 @@ int main(int argc, char **argv) > { "dig-holes", no_argument, NULL, 'd' }, > { "insert-range", no_argument, NULL, 'i' }, > { "zero-range", no_argument, NULL, 'z' }, > + { "write-zeroes", no_argument, NULL, 'w' }, > { "offset", required_argument, NULL, 'o' }, > { "length", required_argument, NULL, 'l' }, > { "posix", no_argument, NULL, 'x' }, > @@ -312,8 +318,8 @@ int main(int argc, char **argv) > }; > > static const ul_excl_t excl[] = { /* rows and cols in ASCII order */ > - { 'c', 'd', 'i', 'p', 'x', 'z'}, > - { 'c', 'i', 'n', 'x' }, > + { 'c', 'd', 'i', 'p', 'w', 'x', 'z'}, > + { 'c', 'i', 'n', 'w', 'x' }, > { 0 } > }; > int excl_st[ARRAY_SIZE(excl)] = UL_EXCL_STATUS_INIT; > @@ -323,7 +329,7 @@ int main(int argc, char **argv) > textdomain(PACKAGE); > close_stdout_atexit(); > > - while ((c = getopt_long(argc, argv, "hvVncpdizxl:o:", longopts, NULL)) > + while ((c = getopt_long(argc, argv, "hvVncpdizwxl:o:", longopts, NULL)) > != -1) { > > err_exclusive_options(c, longopts, excl, excl_st); > @@ -353,6 +359,9 @@ int main(int argc, char **argv) > case 'z': > mode |= FALLOC_FL_ZERO_RANGE; > break; > + case 'w': > + mode |= FALLOC_FL_WRITE_ZEROES; > + break; > case 'x': > #ifdef HAVE_POSIX_FALLOCATE > posix = 1; > @@ -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. :) --D > + filename, str, length); > else > fprintf(stdout, _("%s: %s (%ju bytes) allocated.\n"), > filename, str, length); > -- > 2.39.2 > >