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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <1428e3fe-ae7a-410d-97b5-7dd0249c41c0@huaweicloud.com>
Date: Fri, 15 Aug 2025 17:59:01 +0800
From: Zhang Yi <yi.zhang@...weicloud.com>
To: "Darrick J. Wong" <djwong@...nel.org>
Cc: 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,
 linux-kernel@...r.kernel.org, linux-api@...r.kernel.org, hch@....de,
 tytso@....edu, bmarzins@...hat.com, chaitanyak@...dia.com,
 shinichiro.kawasaki@....com, brauner@...nel.org, martin.petersen@...cle.com,
 yi.zhang@...wei.com, chengzhihao1@...wei.com, yukuai3@...wei.com,
 yangerkun@...wei.com
Subject: Re: [PATCH xfsprogs v2] xfs_io: add FALLOC_FL_WRITE_ZEROES support

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.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;
> 
> 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.

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
>>
>>