linux-ext4 - Re: [PATCH] Ext4: Don't normalize an falloc request if it can fit in 1 extent.

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: <CABFC-fM8pMoJ=hUKOixNkva98P6_XD5PxXq3Tq0vE+5u-iEz3A@mail.gmail.com>
Date:	Fri, 28 Oct 2011 12:05:30 -0700
From:	Greg Harm <gharm@...gle.com>
To:	Andreas Dilger <aedilger@...il.com>
Cc:	"Theodore Ts'o" <tytso@....edu>,
	Andreas Dilger <adilger.kernel@...ger.ca>,
	"linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH] Ext4: Don't normalize an falloc request if it can fit in
 1 extent.

On Fri, Oct 28, 2011 at 11:47 AM, Andreas Dilger <aedilger@...il.com> wrote:
> On 2011-10-28, at 12:01 PM, Greg Harm <gharm@...gle.com> wrote:
>> If an fallocate request fits in EXT_UNINIT_MAX_LEN, then set the
>> EXT4_GET_BLOCKS_NO_NORMALIZE flag. For larger fallocate requests,
>> let mballoc.c normalize the request.
>> This fixes a problem where large requests were being split
>> into non-contiguous extents due to haldar@...gle.com's
>> "ext4: do not normalize block requests from fallocate."
>>
>> Testing: Checked that 8.x MB falloc'ed files are still laid down
>> next to each other (contiguously).
>> Checked that the maximum size extent (127.9MB) is allocated as 1
>> extent.
>> Checked that a 1GB file is somewhat contiguous (often 5-6
>> non-contiguous extents now).
>> Checked that a 120MB file can still be falloc'ed even if there are no
>> single extents large enough to hold it.
>
> It would be great to add these test cases to xfstests so that this doesn't break in the future.
Hi Andreas,

I totally agree. I have that on my TODO list (but no current ETA).

Thanks,
Greg

>> Signed-off-by: Greg Harm <gharm@...gle.com>
>> ---
>> fs/ext4/extents.c |   13 ++++++++++---
>> 1 files changed, 10 insertions(+), 3 deletions(-)
>>
>> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
>> index 57cf568..9819216 100644
>> --- a/fs/ext4/extents.c
>> +++ b/fs/ext4/extents.c
>> @@ -3761,6 +3761,7 @@ long ext4_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
>>    int ret2 = 0;
>>    int retries = 0;
>>    struct ext4_map_blocks map;
>> +    int map_blocks_flags;
>>    unsigned int credits, blkbits = inode->i_blkbits;
>>
>>    /*
>> @@ -3805,9 +3806,15 @@ retry:
>>            ret = PTR_ERR(handle);
>>            break;
>>        }
>> -        ret = ext4_map_blocks(handle, inode, &map,
>> -                      EXT4_GET_BLOCKS_CREATE_UNINIT_EXT |
>> -                      EXT4_GET_BLOCKS_NO_NORMALIZE);
>> +        map_blocks_flags = EXT4_GET_BLOCKS_CREATE_UNINIT_EXT;
>> +        /*
>> +         * Don't normalize the request if it can fit in one extent so
>> +         * that it doesn't get unnecessarily split into multiple
>> +         * extents.
>> +         */
>> +        if (len <= EXT_UNINIT_MAX_LEN << blkbits)
>> +            map_blocks_flags |= EXT4_GET_BLOCKS_NO_NORMALIZE;
>> +        ret = ext4_map_blocks(handle, inode, &map, map_blocks_flags);
>>        if (ret <= 0) {
>> #ifdef EXT4FS_DEBUG
>>            WARN_ON(ret <= 0);
>> --
>> 1.7.3.1
>>
>
--
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