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Message-ID: <309d082f-45b9-9dac-9921-6c3d44de17a7@huaweicloud.com>
Date: Thu, 28 Sep 2023 11:31:21 +0800
From: Kemeng Shi <shikemeng@...weicloud.com>
To: Ritesh Harjani <ritesh.list@...il.com>, tytso@....edu,
adilger.kernel@...ger.ca
Cc: ojaswin@...ux.ibm.com, linux-ext4@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 02/12] ext4: factor out codes to update block bitmap
and group descriptor on disk from ext4_mb_mark_bb
on 9/27/2023 4:49 PM, Ritesh Harjani wrote:
> Kemeng Shi <shikemeng@...weicloud.com> writes:
>
>> There are several reasons to add a general function ext4_mb_mark_context
>> to update block bitmap and group descriptor on disk:
>> 1. pair behavior of alloc/free bits. For example,
>> ext4_mb_new_blocks_simple will update free_clusters in struct flex_groups
>> in ext4_mb_mark_bb while ext4_free_blocks_simple forgets this.
>> 2. remove repeat code to read from disk, update and write back to disk.
>> 3. reduce future unit test mocks to catch real IO to update structure
>> on disk.
>>
>> Signed-off-by: Kemeng Shi <shikemeng@...weicloud.com>
>> ---
>> fs/ext4/mballoc.c | 147 ++++++++++++++++++++++++----------------------
>> 1 file changed, 77 insertions(+), 70 deletions(-)
>>
>> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
>> index cf09adfbaf11..e1320eea46e9 100644
>> --- a/fs/ext4/mballoc.c
>> +++ b/fs/ext4/mballoc.c
>> @@ -3953,6 +3953,80 @@ void ext4_exit_mballoc(void)
>> ext4_groupinfo_destroy_slabs();
>> }
>>
>> +static int
>> +ext4_mb_mark_context(struct super_block *sb, bool state, ext4_group_t group,
>> + ext4_grpblk_t blkoff, ext4_grpblk_t len)
>
>
> ext4_grpblk_t is defined as int.
> /* data type for block offset of block group */
> typedef int ext4_grpblk_t;
>
> I think len should be unsigned int (u32) here.
>
Hi Ritesh, thanks for reply and a lot suggestions to this patch and other
patches in this series.
I define len as ext4_grpblk_t as I think ext4_grpblk_t is supposed to fit
block or cluster number of single group.
Here are some examples save block number of group to ext4_grpblk_t:
static ext4_fsblk_t ext4_valid_block_bitmap(...)
{
...
ext4_grpblk_t max_bit = EXT4_CLUSTERS_PER_GROUP(sb);
...
}
static ext4_fsblk_t ext4_mb_new_blocks_simple(...)
{
...
ext4_grpblk_t max = EXT4_CLUSTERS_PER_GROUP(sb);
...
}
/* len could be group block number if group has only one fragment */
static int mb_avg_fragment_size_order(..., ext4_grpblk_t len)
As ext4_grpblk_t is data type for block offset of block group, so
ext4_grpblk_t fits "block number of group" - 1. If we support block
number of group > INT_MAX + 1, ext4_grpblk_t should be unsigned int anyway.
IMO, it's more simple just make ext4_grpblk_t data type for block number
in a single group and make it unsigned int if block number of group is
possible to >= INT_MAX + 1. Does this makes to you.
>> +{
>> + struct ext4_sb_info *sbi = EXT4_SB(sb);
>> + struct buffer_head *bitmap_bh = NULL;
>> + struct ext4_group_desc *gdp;
>> + struct buffer_head *gdp_bh;
>> + int err;
>> + unsigned int i, already, changed;
>> +
>> + bitmap_bh = ext4_read_block_bitmap(sb, group);
>> + if (IS_ERR(bitmap_bh))
>> + return PTR_ERR(bitmap_bh);
>> +
>> + err = -EIO;
>> + gdp = ext4_get_group_desc(sb, group, &gdp_bh);
>> + if (!gdp)
>> + goto out_err;
>> +
>> + ext4_lock_group(sb, group);
>> + if (ext4_has_group_desc_csum(sb) &&
>> + (gdp->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT))) {
>> + gdp->bg_flags &= cpu_to_le16(~EXT4_BG_BLOCK_UNINIT);
>> + ext4_free_group_clusters_set(sb, gdp,
>> + ext4_free_clusters_after_init(sb, group, gdp));
>> + }
>> +
>> + already = 0;
>> + for (i = 0; i < len; i++)
>> + if (mb_test_bit(blkoff + i, bitmap_bh->b_data) ==
>> + state)
>> + already++;
>> + changed = len - already;
>> +
>> + if (state) {
>> + mb_set_bits(bitmap_bh->b_data, blkoff, len);
>> + ext4_free_group_clusters_set(sb, gdp,
>> + ext4_free_group_clusters(sb, gdp) - changed);
>> + } else {
>> + mb_clear_bits(bitmap_bh->b_data, blkoff, len);
>> + ext4_free_group_clusters_set(sb, gdp,
>> + ext4_free_group_clusters(sb, gdp) + changed);
>> + }
>> +
>> + ext4_block_bitmap_csum_set(sb, gdp, bitmap_bh);
>> + ext4_group_desc_csum_set(sb, group, gdp);
>> + ext4_unlock_group(sb, group);
>> +
>> + if (sbi->s_log_groups_per_flex) {
>> + ext4_group_t flex_group = ext4_flex_group(sbi, group);
>> + struct flex_groups *fg = sbi_array_rcu_deref(sbi,
>> + s_flex_groups, flex_group);
>> +
>> + if (state)
>> + atomic64_sub(changed, &fg->free_clusters);
>> + else
>> + atomic64_add(changed, &fg->free_clusters);
>> + }
>> +
>> + err = ext4_handle_dirty_metadata(NULL, NULL, bitmap_bh);
>> + if (err)
>> + goto out_err;
>> + err = ext4_handle_dirty_metadata(NULL, NULL, gdp_bh);
>> + if (err)
>> + goto out_err;
>> +
>> + sync_dirty_buffer(bitmap_bh);
>> + sync_dirty_buffer(gdp_bh);
>> +
>> +out_err:
>> + brelse(bitmap_bh);
>> + return err;
>> +}
>>
>> /*
>> * Check quota and mark chosen space (ac->ac_b_ex) non-free in bitmaps
>> @@ -4079,15 +4153,11 @@ ext4_mb_mark_diskspace_used(struct ext4_allocation_context *ac,
>> void ext4_mb_mark_bb(struct super_block *sb, ext4_fsblk_t block,
>> int len, bool state)
>
> Even ext4_mb_mark_bb should take len as unsigned int IMO.
> For e.g. ext4_fc_replay_add_range() passes map.m_len which is also
> unsigned int.
If we agree ext4_grpblk_t to be data type for block number in group,
I think it's more reasonable to take len as ext4_grpblk_t too.
Look forward to you reply. Thanks!
>
>
> Otherwise the patch looks good to me. Feel free to add -
>
> Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@...il.com>
>
> -ritesh
>
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