linux-ext4 - Question about extents.c/ext4_ext_punch

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-next>] [day] [month] [year] [list]

Message-ID: <5002BFAE.9030408@gmail.com>
Date:	Sun, 15 Jul 2012 21:03:42 +0800
From:	Wang Sheng-Hui <shhuiw@...il.com>
To:	Allison Henderson <achender@...ux.vnet.ibm.com>,
	Lukas Czerner <lczerner@...hat.com>,
	"Theodore Ts'o" <tytso@....edu>, linux-ext4@...r.kernel.org
Subject: Question about extents.c/ext4_ext_punch_hole

Dear all,

I'm reading the code of extents.c, and confused by the function "ext4_ext_punch_hole".

In my understanding, if we want to punch hole for the range (loff_t offset, loff_t length),
then we finally will get one hole block-size aligned, right?

[code in ext4_ext_punch_hole]
	first_block = (offset + sb->s_blocksize - 1) >>
		EXT4_BLOCK_SIZE_BITS(sb);
	stop_block = (offset + length) >> EXT4_BLOCK_SIZE_BITS(sb);
[code]

>From the code, we'll get one hole range contained in the range [offset, length+offset-1].

For example, we set the block size to 1K, and we specify the range [offset:1000, offset:2000].
Then we'll get first_block:1,stop_block:2, with some head/tail range ignored.
      {-23------|===========|----952---}
     1000      1024       2048        2999
     offset                        offset+length-1
'==='means punched hole here.

Please correct me if I'm wrong.


Regards,
--
To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html