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.
> 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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