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Message-ID: <daa4430a-bd26-1b0b-eaf7-928b3af9b601@huaweicloud.com>
Date: Sun, 14 May 2023 19:57:05 +0800
From: Kemeng Shi <shikemeng@...weicloud.com>
To: Ojaswin Mujoo <ojaswin@...ux.ibm.com>
Cc: tytso@....edu, adilger.kernel@...ger.ca,
linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 15/19] ext4: call ext4_mb_mark_group_bb in
ext4_mb_mark_diskspace_used
on 5/14/2023 5:37 PM, Ojaswin Mujoo wrote:
> On Mon, Apr 17, 2023 at 07:06:13PM +0800, Kemeng Shi wrote:
>> call ext4_mb_mark_group_bb in ext4_mb_mark_diskspace_used to:
>> 1. remove repeat code to normally update bitmap and group descriptor
>> on disk.
>> 2. call ext4_mb_mark_group_bb instead of only setting bits in block bitmap
>> to fix the bitmap. Function ext4_mb_mark_group_bb will also update
>> checksum of bitmap and other counter along with the bit change to keep
>> the cosistent with bit change or block bitmap will be marked corrupted as
>> checksum of bitmap is in inconsistent state.
>>
>> Signed-off-by: Kemeng Shi <shikemeng@...weicloud.com>
>
> Looks good, feel free to add:
>
> Reviewed-by: Ojaswin Mujoo <ojaswin@...ux.ibm.com>
>
> Just a minor suggestion below:
>> ---
>> fs/ext4/mballoc.c | 90 +++++++++++++----------------------------------
>> 1 file changed, 24 insertions(+), 66 deletions(-)
>>
>> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
>> index c3e620f6eded..bd440614db76 100644
>> --- a/fs/ext4/mballoc.c
>> +++ b/fs/ext4/mballoc.c
>> @@ -3846,9 +3846,12 @@ static noinline_for_stack int
>> ext4_mb_mark_diskspace_used(struct ext4_allocation_context *ac,
>> handle_t *handle, unsigned int reserv_clstrs)
>> {
>> - struct buffer_head *bitmap_bh = NULL;
>> + struct ext4_mark_context mc = {
>> + .handle = handle,
>> + .sb = ac->ac_sb,
>> + .state = 1,
>> + };
>> struct ext4_group_desc *gdp;
>> - struct buffer_head *gdp_bh;
>> struct ext4_sb_info *sbi;
>> struct super_block *sb;
>> ext4_fsblk_t block;
>> @@ -3860,32 +3863,13 @@ ext4_mb_mark_diskspace_used(struct ext4_allocation_context *ac,
>> sb = ac->ac_sb;
>> sbi = EXT4_SB(sb);
>>
>> - bitmap_bh = ext4_read_block_bitmap(sb, ac->ac_b_ex.fe_group);
>> - if (IS_ERR(bitmap_bh)) {
>> - return PTR_ERR(bitmap_bh);
>> - }
>> -
>> - BUFFER_TRACE(bitmap_bh, "getting write access");
>> - err = ext4_journal_get_write_access(handle, sb, bitmap_bh,
>> - EXT4_JTR_NONE);
>> - if (err)
>> - goto out_err;
>> -
>> - err = -EIO;
>> - gdp = ext4_get_group_desc(sb, ac->ac_b_ex.fe_group, &gdp_bh);
>> + gdp = ext4_get_group_desc(sb, ac->ac_b_ex.fe_group, NULL);
>> if (!gdp)
>> - goto out_err;
>> -
>> + return -EIO;
>> ext4_debug("using block group %u(%d)\n", ac->ac_b_ex.fe_group,
>> ext4_free_group_clusters(sb, gdp));
>>
>> - BUFFER_TRACE(gdp_bh, "get_write_access");
>> - err = ext4_journal_get_write_access(handle, sb, gdp_bh, EXT4_JTR_NONE);
>> - if (err)
>> - goto out_err;
>> -
>> block = ext4_grp_offs_to_block(sb, &ac->ac_b_ex);
>> -
>> len = EXT4_C2B(sbi, ac->ac_b_ex.fe_len);
>> if (!ext4_inode_block_valid(ac->ac_inode, block, len)) {
>> ext4_error(sb, "Allocating blocks %llu-%llu which overlap "
>> @@ -3894,41 +3878,30 @@ ext4_mb_mark_diskspace_used(struct ext4_allocation_context *ac,
>> * Fix the bitmap and return EFSCORRUPTED
>> * We leak some of the blocks here.
>> */
>> - ext4_lock_group(sb, ac->ac_b_ex.fe_group);
>> - mb_set_bits(bitmap_bh->b_data, ac->ac_b_ex.fe_start,
>> - ac->ac_b_ex.fe_len);
>> - ext4_unlock_group(sb, ac->ac_b_ex.fe_group);
>> - err = ext4_handle_dirty_metadata(handle, NULL, bitmap_bh);
>> + err = ext4_mb_mark_group_bb(&mc, ac->ac_b_ex.fe_group,
>> + ac->ac_b_ex.fe_start,
>> + ac->ac_b_ex.fe_len,
>> + 0);
>> if (!err)
>> err = -EFSCORRUPTED;
>> - goto out_err;
>> + return err;
>> }
>>
>> - ext4_lock_group(sb, ac->ac_b_ex.fe_group);
>> #ifdef AGGRESSIVE_CHECK
>> - {
>> - int i;
>> - for (i = 0; i < ac->ac_b_ex.fe_len; i++) {
>> - BUG_ON(mb_test_bit(ac->ac_b_ex.fe_start + i,
>> - bitmap_bh->b_data));
>> - }
>> - }
>> + err = ext4_mb_mark_group_bb(&mc, ac->ac_b_ex.fe_group,
>> + ac->ac_b_ex.fe_start, ac->ac_b_ex.fe_len,
>> + EXT4_MB_BITMAP_MARKED_CHECK);
>> +#else
>> + err = ext4_mb_mark_group_bb(&mc, ac->ac_b_ex.fe_group,
>> + ac->ac_b_ex.fe_start, ac->ac_b_ex.fe_len,
>> + 0);
>> #endif
>
> I think, the refactoring the AGGRESSIVE_CHECK as follows makes the
> intent more obvious and easier to read.
>
> #ifdef AGGRESSIVE_CHECK
>
> flags |= EXT4_MB_BITMAP_MARKED_CHECK;
>
> #endif
>
> err = ext4_mb_mark_group_bb(&mc, ac->ac_b_ex.fe_group,
> ac->ac_b_ex.fe_start, ac->ac_b_ex.fe_len,
> flags);
Although this will add a new flags variable declartion, the AGGRESSIVE_CHECK code
looks much better. Thanks for the suggestion, I will refactoring AGGRESSIVE_CHECK
in this way in this patch and patch 16.
> Regards,
> ojaswin
>
>> - mb_set_bits(bitmap_bh->b_data, ac->ac_b_ex.fe_start,
>> - ac->ac_b_ex.fe_len);
>> - 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,
>> - ac->ac_b_ex.fe_group, gdp));
>> - }
>> - len = ext4_free_group_clusters(sb, gdp) - ac->ac_b_ex.fe_len;
>> - ext4_free_group_clusters_set(sb, gdp, len);
>> - ext4_block_bitmap_csum_set(sb, gdp, bitmap_bh);
>> - ext4_group_desc_csum_set(sb, ac->ac_b_ex.fe_group, gdp);
>> + if (err && mc.changed == 0)
>> + return err;
>>
>> - ext4_unlock_group(sb, ac->ac_b_ex.fe_group);
>> +#ifdef AGGRESSIVE_CHECK
>> + BUG_ON(mc.changed != ac->ac_b_ex.fe_len);
>> +#endif
>> percpu_counter_sub(&sbi->s_freeclusters_counter, ac->ac_b_ex.fe_len);
>> /*
>> * Now reduce the dirty block count also. Should not go negative
>> @@ -3938,21 +3911,6 @@ ext4_mb_mark_diskspace_used(struct ext4_allocation_context *ac,
>> percpu_counter_sub(&sbi->s_dirtyclusters_counter,
>> reserv_clstrs);
>>
>> - if (sbi->s_log_groups_per_flex) {
>> - ext4_group_t flex_group = ext4_flex_group(sbi,
>> - ac->ac_b_ex.fe_group);
>> - atomic64_sub(ac->ac_b_ex.fe_len,
>> - &sbi_array_rcu_deref(sbi, s_flex_groups,
>> - flex_group)->free_clusters);
>> - }
>> -
>> - err = ext4_handle_dirty_metadata(handle, NULL, bitmap_bh);
>> - if (err)
>> - goto out_err;
>> - err = ext4_handle_dirty_metadata(handle, NULL, gdp_bh);
>> -
>> -out_err:
>> - brelse(bitmap_bh);
>> return err;
>> }
>>
>> --
>> 2.30.0
>>
>
--
Best wishes
Kemeng Shi
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