Kemeng Shi <shikemeng@xxxxxxxxxxxxxxx> writes:
Hello Kemeng,
> There are several reasons to add a general function to update block
> bitmap and group descriptor on disk:
... named ext4_mb_mark_context(<params>)
> 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@xxxxxxxxxxxxxxx>
> Reviewed-by: Ojaswin Mujoo <ojaswin@xxxxxxxxxxxxx>
> ---
> fs/ext4/mballoc.c | 169 +++++++++++++++++++++++++++-------------------
> 1 file changed, 99 insertions(+), 70 deletions(-)
>
> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
> index c91db9f57524..e2be572deb75 100644
> --- a/fs/ext4/mballoc.c
> +++ b/fs/ext4/mballoc.c
> @@ -3952,6 +3952,100 @@ void ext4_exit_mballoc(void)
> ext4_groupinfo_destroy_slabs();
> }
>
> +/*
> + * Collect global setting to reduce the number of variable passing to
> + * ext4_mb_mark_context. Pass target group blocks range directly to
> + * reuse the prepared global setting for multiple block ranges and
> + * to show clearly the specific block range will be marked.
> + */
> +struct ext4_mark_context {
> + struct super_block *sb;
> + int state;
> +};
This structure definition does not reflect of it's naming.
Why can't we also add cblk & clen, flags to it?
I think the idea of defining a new function named
ext4_mb_prepare_mark_context() was that we can prepare "struct ext4_mark_context"
with different cblk, clen & flags arguments for cases where we might
have to call ext4_mb_mark_context() more than once in the same function
or call ext4_mb_mark_context() anywhere but at the start of the function.
As I see it in the current series, we are calling
ext4_mb_prepare_mark_context() at the start of every function. Just for
this purpose we don't need an extra function, right? That we can directly do
at the time of declaring a structure variable itself (like how you did
in previous version)
What do you think of the approach where we add cblk, clen & flags
variables to ext4_mark_context()? Do you see any problems/difficulties
with that design?
> +
> +static inline void ext4_mb_prepare_mark_context(struct ext4_mark_context *mc,
> + struct super_block *sb,
> + int state)
> +{
> + mc->sb = sb;
> + mc->state = state;
> +}
> +
> +static int
> +ext4_mb_mark_context(struct ext4_mark_context *mc, ext4_group_t group,
> + ext4_grpblk_t blkoff, ext4_grpblk_t len)
> +{
> + struct super_block *sb = mc->sb;
> + 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) ==
> + mc->state)
> + already++;
> + changed = len - already;
> +
> + if (mc->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 (mc->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
> @@ -4078,16 +4172,14 @@ 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, int state)
> {
> - struct buffer_head *bitmap_bh = NULL;
> - struct ext4_group_desc *gdp;
> - struct buffer_head *gdp_bh;
> + struct ext4_mark_context mc;
> struct ext4_sb_info *sbi = EXT4_SB(sb);
> ext4_group_t group;
> ext4_grpblk_t blkoff;
> - int i, err = 0;
> - int already;
> - unsigned int clen, clen_changed, thisgrp_len;
> + int err = 0;
> + unsigned int clen, thisgrp_len;
>
> + ext4_mb_prepare_mark_context(&mc, sb, state);
> while (len > 0) {
> ext4_get_group_no_and_offset(sb, block, &group, &blkoff);
>
> @@ -4107,80 +4199,17 @@ void ext4_mb_mark_bb(struct super_block *sb, ext4_fsblk_t block,
> ext4_error(sb, "Marking blocks in system zone - "
> "Block = %llu, len = %u",
> block, thisgrp_len);
> - bitmap_bh = NULL;
> - break;
> - }
> -
> - bitmap_bh = ext4_read_block_bitmap(sb, group);
> - if (IS_ERR(bitmap_bh)) {
> - err = PTR_ERR(bitmap_bh);
> - bitmap_bh = NULL;
> break;
> }
>
> - err = -EIO;
> - gdp = ext4_get_group_desc(sb, group, &gdp_bh);
> - if (!gdp)
> - break;
> -
> - ext4_lock_group(sb, group);
> - already = 0;
> - for (i = 0; i < clen; i++)
> - if (!mb_test_bit(blkoff + i, bitmap_bh->b_data) ==
> - !state)
> - already++;
> -
> - clen_changed = clen - already;
> - if (state)
> - mb_set_bits(bitmap_bh->b_data, blkoff, clen);
> - else
> - mb_clear_bits(bitmap_bh->b_data, blkoff, clen);
> - 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));
> - }
> - if (state)
> - clen = ext4_free_group_clusters(sb, gdp) - clen_changed;
> - else
> - clen = ext4_free_group_clusters(sb, gdp) + clen_changed;
> -
> - ext4_free_group_clusters_set(sb, gdp, clen);
> - 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(clen_changed, &fg->free_clusters);
> - else
> - atomic64_add(clen_changed, &fg->free_clusters);
> -
> - }
> -
> - err = ext4_handle_dirty_metadata(NULL, NULL, bitmap_bh);
> - if (err)
> - break;
> - sync_dirty_buffer(bitmap_bh);
> - err = ext4_handle_dirty_metadata(NULL, NULL, gdp_bh);
> - sync_dirty_buffer(gdp_bh);
> + err = ext4_mb_mark_context(&mc, group, blkoff, clen);
> if (err)
> break;
>
> block += thisgrp_len;
> len -= thisgrp_len;
> - brelse(bitmap_bh);
> BUG_ON(len < 0);
> }
> -
> - if (err)
> - brelse(bitmap_bh);
> }
>
> /*
> --
> 2.30.0
-ritesh
