On Fri, Oct 28, 2011 at 11:47 AM, Andreas Dilger <aedilger@xxxxxxxxx> wrote:
> On 2011-10-28, at 12:01 PM, Greg Harm <gharm@xxxxxxxxxx> 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@xxxxxxxxxx'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@xxxxxxxxxx>
>> ---
>> 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
>>
>
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