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Date: Tue, 19 Apr 2011 22:16:03 +0300
From: Amir Goldstein <amir73il@...il.com>
To: Lukas Czerner <lczerner@...hat.com>
Cc: linux-ext4@...r.kernel.org, tytso@....edu
Subject: Re: [PATCH] ext4: ext4_trim_fs() load buddy only when it is needed
On Mon, Apr 18, 2011 at 7:32 PM, Lukas Czerner <lczerner@...hat.com> wrote:
> Currently we are loading buddy ext4_mb_load_buddy() for every block
> group we are going through in ext4_trim_fs() in many cases just to find
> out that there is not enough space to be bothered with. As Amir Goldstein
> suggested we can use bb_free information directly from ext4_group_info.
>
> This commit removes ext4_mb_load_buddy() from ext4_trim_fs() and rather
> get the ext4_group_info via ext4_get_group_info() and use the bb_free
> information directly from that. This avoids unnecessary call to load
> buddy in the case the group does not have enough free space to trim.
> Loading buddy is now moved to ext4_trim_all_free().
>
> Tested by me with xfstests 251.
>
> Signed-off-by: Lukas Czerner <lczerner@...hat.com>
> ---
> fs/ext4/mballoc.c | 48 ++++++++++++++++++++++++++----------------------
> 1 files changed, 26 insertions(+), 22 deletions(-)
>
> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
> index d8a16ee..776d7a8 100644
> --- a/fs/ext4/mballoc.c
> +++ b/fs/ext4/mballoc.c
> @@ -4760,20 +4760,25 @@ static int ext4_trim_extent(struct super_block *sb, int start, int count,
> * the group buddy bitmap. This is done until whole group is scanned.
> */
> static ext4_grpblk_t
> -ext4_trim_all_free(struct super_block *sb, struct ext4_buddy *e4b,
> - ext4_grpblk_t start, ext4_grpblk_t max, ext4_grpblk_t minblocks)
> +ext4_trim_all_free(struct super_block *sb, ext4_group_t group,
> + ext4_grpblk_t start, ext4_grpblk_t max,
> + ext4_grpblk_t minblocks)
> {
> void *bitmap;
> ext4_grpblk_t next, count = 0;
> - ext4_group_t group;
> + struct ext4_buddy e4b;
> int ret = 0;
>
> - BUG_ON(e4b == NULL);
> + ret = ext4_mb_load_buddy(sb, group, &e4b);
> + if (ret) {
> + ext4_error(sb, "Error in loading buddy "
> + "information for %u", group);
> + return ret;
> + }
>
> - bitmap = e4b->bd_bitmap;
> - group = e4b->bd_group;
> - start = (e4b->bd_info->bb_first_free > start) ?
> - e4b->bd_info->bb_first_free : start;
> + bitmap = e4b.bd_bitmap;
> + start = (e4b.bd_info->bb_first_free > start) ?
> + e4b.bd_info->bb_first_free : start;
not related to the patch, but bb_first_free sound like something that
needs lock_group
protection. I didn't check it though.
other than that, patch looks fine to me.
> ext4_lock_group(sb, group);
>
> while (start < max) {
> @@ -4784,7 +4789,7 @@ ext4_trim_all_free(struct super_block *sb, struct ext4_buddy *e4b,
>
> if ((next - start) >= minblocks) {
> ret = ext4_trim_extent(sb, start,
> - next - start, group, e4b);
> + next - start, group, &e4b);
> if (ret < 0)
> break;
> count += next - start;
> @@ -4802,10 +4807,11 @@ ext4_trim_all_free(struct super_block *sb, struct ext4_buddy *e4b,
> ext4_lock_group(sb, group);
> }
>
> - if ((e4b->bd_info->bb_free - count) < minblocks)
> + if ((e4b.bd_info->bb_free - count) < minblocks)
> break;
> }
> ext4_unlock_group(sb, group);
> + ext4_mb_unload_buddy(&e4b);
>
> ext4_debug("trimmed %d blocks in the group %d\n",
> count, group);
> @@ -4830,11 +4836,11 @@ ext4_trim_all_free(struct super_block *sb, struct ext4_buddy *e4b,
> */
> int ext4_trim_fs(struct super_block *sb, struct fstrim_range *range)
> {
> - struct ext4_buddy e4b;
> + struct ext4_group_info *grp;
> ext4_group_t first_group, last_group;
> ext4_group_t group, ngroups = ext4_get_groups_count(sb);
> ext4_grpblk_t cnt = 0, first_block, last_block;
> - uint64_t start, len, minlen, trimmed;
> + uint64_t start, len, minlen, trimmed = 0;
> ext4_fsblk_t first_data_blk =
> le32_to_cpu(EXT4_SB(sb)->s_es->s_first_data_block);
> int ret = 0;
> @@ -4842,7 +4848,6 @@ int ext4_trim_fs(struct super_block *sb, struct fstrim_range *range)
> start = range->start >> sb->s_blocksize_bits;
> len = range->len >> sb->s_blocksize_bits;
> minlen = range->minlen >> sb->s_blocksize_bits;
> - trimmed = 0;
>
> if (unlikely(minlen > EXT4_BLOCKS_PER_GROUP(sb)))
> return -EINVAL;
> @@ -4863,11 +4868,12 @@ int ext4_trim_fs(struct super_block *sb, struct fstrim_range *range)
> return -EINVAL;
>
> for (group = first_group; group <= last_group; group++) {
> - ret = ext4_mb_load_buddy(sb, group, &e4b);
> - if (ret) {
> - ext4_error(sb, "Error in loading buddy "
> - "information for %u", group);
> - break;
> + grp = ext4_get_group_info(sb, group);
> + /* We only do this if the grp has never been initialized */
> + if (unlikely(EXT4_MB_GRP_NEED_INIT(grp))) {
> + ret = ext4_mb_init_group(sb, group);
> + if (ret)
> + break;
> }
>
> /*
> @@ -4880,16 +4886,14 @@ int ext4_trim_fs(struct super_block *sb, struct fstrim_range *range)
> last_block = first_block + len;
> len -= last_block - first_block;
>
> - if (e4b.bd_info->bb_free >= minlen) {
> - cnt = ext4_trim_all_free(sb, &e4b, first_block,
> + if (grp->bb_free >= minlen) {
> + cnt = ext4_trim_all_free(sb, group, first_block,
> last_block, minlen);
> if (cnt < 0) {
> ret = cnt;
> - ext4_mb_unload_buddy(&e4b);
> break;
> }
> }
> - ext4_mb_unload_buddy(&e4b);
> trimmed += cnt;
> first_block = 0;
> }
> --
> 1.7.4.2
>
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