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 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.zh...@huawei.com> --- v2->v3: - Say less about what the filesystem actually implements as Darrick suggested and clarify the reason why "--keep-size" cannot be used together in the man page. - Modify the verbose output message. 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..a06cf7a50 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 == SYNOPSIS -*fallocate* [*-c*|*-p*|*-z*] [*-o* _offset_] *-l* _length_ [*-n*] _filename_ +*fallocate* [*-c*|*-p*|*-z*|*-w*] [*-o* _offset_] *-l* _length_ [*-n*] _filename_ *fallocate* *-d* [*-o* _offset_] [*-l* _length_] _filename_ @@ -28,7 +28,7 @@ The exit status returned by *fallocate* is 0 on success and 1 on failure. The _length_ and _offset_ arguments may be followed by the multiplicative suffixes KiB (=1024), MiB (=1024*1024), and so on for GiB, TiB, PiB, EiB, ZiB, and YiB (the "iB" is optional, e.g., "K" has the same meaning as "KiB") or the suffixes KB (=1000), MB (=1000*1000), and so on for GB, TB, PB, EB, ZB, and YB. -The options *--collapse-range*, *--dig-holes*, *--punch-hole*, *--zero-range* and *--posix* are mutually exclusive. +The options *--collapse-range*, *--dig-holes*, *--punch-hole*, *--zero-range*, *--write-zeroes* and *--posix* are mutually exclusive. *-c*, *--collapse-range*:: Removes a byte range from a file, without leaving a hole. The byte range to be collapsed starts at _offset_ and continues for _length_ bytes. At the completion of the operation, the contents of the file starting at the location __offset__+_length_ will be appended at the location _offset_, and the file will be _length_ bytes smaller. The option *--keep-size* may not be specified for the collapse-range operation. @@ -76,6 +76,13 @@ Option *--keep-size* can be specified to prevent file length modification. + Available since Linux 3.14 for ext4 (only for extent-based files) and XFS. +*-w*, *--write-zeroes*:: +Zeroes space in the byte range starting at _offset_ and continuing for _length_ bytes. Within the specified range, written 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 and subsequent writes to that range do not require further changes to the file mapping metadata. ++ +Zeroing is done within the filesystem. The filesystem may use a hardware-accelerated zeroing command or may submit regular writes. The behavior depends on the filesystem design and the available hardware. ++ +Options *--keep-size* can not be specified for the write-zeroes operation because allocating written blocks beyond the inode size is not permitted. + include::man-common/help-version.adoc[] == AUTHORS diff --git a/sys-utils/fallocate.c b/sys-utils/fallocate.c index 13bf52915..afd615537 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) written as zeroes.\n"), + filename, str, length); else fprintf(stdout, _("%s: %s (%ju bytes) allocated.\n"), filename, str, length); -- 2.39.2
