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Date:   Thu, 25 Feb 2021 18:36:30 -0800
From:   harshad shirwadkar <harshadshirwadkar@...il.com>
To:     Благодаренко Артём 
        <artem.blagodarenko@...il.com>
Cc:     Ext4 Developers List <linux-ext4@...r.kernel.org>,
        "Theodore Y. Ts'o" <tytso@....edu>,
        Alex Zhuravlev <bzzz@...mcloud.com>,
        Shuichi Ihara <sihara@....com>,
        Andreas Dilger <adilger@...ger.ca>
Subject: Re: [PATCH v2 3/5] ext4: add MB_NUM_ORDERS macro

Thanks Artem for pointing that out. I'll fix this in V3.

- Harshad

On Tue, Feb 16, 2021 at 2:45 AM Благодаренко Артём
<artem.blagodarenko@...il.com> wrote:
>
> Hello Harshad,
>
> I believe there are two places yet there number could be changed to the macros
>
> fs/ext4/mballoc.c <<ext4_mb_init_cache>>
>              (sb->s_blocksize_bits+2));
>
> fs/ext4/mballoc.c <<ext4_mb_good_group>>
> if (ac->ac_2order > ac->ac_sb->s_blocksize_bits+1)
>
> Best regards,
> Artem Blagodarenko
>
> > On 9 Feb 2021, at 23:28, Harshad Shirwadkar <harshadshirwadkar@...il.com> wrote:
> >
> > A few arrays in mballoc.c use the total number of valid orders as
> > their size. Currently, this value is set as "sb->s_blocksize_bits +
> > 2". This makes code harder to read. So, instead add a new macro
> > MB_NUM_ORDERS(sb) to make the code more readable.
> >
> > Signed-off-by: Harshad Shirwadkar <harshadshirwadkar@...il.com>
> > Reviewed-by: Andreas Dilger <adilger@...ger.ca>
> > ---
> > fs/ext4/mballoc.c | 15 ++++++++-------
> > fs/ext4/mballoc.h |  5 +++++
> > 2 files changed, 13 insertions(+), 7 deletions(-)
> >
> > diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
> > index fffd0770e930..b7f25120547d 100644
> > --- a/fs/ext4/mballoc.c
> > +++ b/fs/ext4/mballoc.c
> > @@ -756,7 +756,7 @@ mb_set_largest_free_order(struct super_block *sb, struct ext4_group_info *grp)
> >
> >       grp->bb_largest_free_order = -1; /* uninit */
> >
> > -     bits = sb->s_blocksize_bits + 1;
> > +     bits = MB_NUM_ORDERS(sb) - 1;
> >       for (i = bits; i >= 0; i--) {
> >               if (grp->bb_counters[i] > 0) {
> >                       grp->bb_largest_free_order = i;
> > @@ -1928,7 +1928,7 @@ void ext4_mb_simple_scan_group(struct ext4_allocation_context *ac,
> >       int max;
> >
> >       BUG_ON(ac->ac_2order <= 0);
> > -     for (i = ac->ac_2order; i <= sb->s_blocksize_bits + 1; i++) {
> > +     for (i = ac->ac_2order; i < MB_NUM_ORDERS(sb); i++) {
> >               if (grp->bb_counters[i] == 0)
> >                       continue;
> >
> > @@ -2314,13 +2314,13 @@ ext4_mb_regular_allocator(struct ext4_allocation_context *ac)
> >        * We also support searching for power-of-two requests only for
> >        * requests upto maximum buddy size we have constructed.
> >        */
> > -     if (i >= sbi->s_mb_order2_reqs && i <= sb->s_blocksize_bits + 2) {
> > +     if (i >= sbi->s_mb_order2_reqs && i <= MB_NUM_ORDERS(sb)) {
> >               /*
> >                * This should tell if fe_len is exactly power of 2
> >                */
> >               if ((ac->ac_g_ex.fe_len & (~(1 << (i - 1)))) == 0)
> >                       ac->ac_2order = array_index_nospec(i - 1,
> > -                                                        sb->s_blocksize_bits + 2);
> > +                                                        MB_NUM_ORDERS(sb));
> >       }
> >
> >       /* if stream allocation is enabled, use global goal */
> > @@ -2850,7 +2850,7 @@ int ext4_mb_init(struct super_block *sb)
> >       unsigned max;
> >       int ret;
> >
> > -     i = (sb->s_blocksize_bits + 2) * sizeof(*sbi->s_mb_offsets);
> > +     i = MB_NUM_ORDERS(sb) * sizeof(*sbi->s_mb_offsets);
> >
> >       sbi->s_mb_offsets = kmalloc(i, GFP_KERNEL);
> >       if (sbi->s_mb_offsets == NULL) {
> > @@ -2858,7 +2858,7 @@ int ext4_mb_init(struct super_block *sb)
> >               goto out;
> >       }
> >
> > -     i = (sb->s_blocksize_bits + 2) * sizeof(*sbi->s_mb_maxs);
> > +     i = MB_NUM_ORDERS(sb) * sizeof(*sbi->s_mb_maxs);
> >       sbi->s_mb_maxs = kmalloc(i, GFP_KERNEL);
> >       if (sbi->s_mb_maxs == NULL) {
> >               ret = -ENOMEM;
> > @@ -2884,7 +2884,8 @@ int ext4_mb_init(struct super_block *sb)
> >               offset_incr = offset_incr >> 1;
> >               max = max >> 1;
> >               i++;
> > -     } while (i <= sb->s_blocksize_bits + 1);
> > +     } while (i < MB_NUM_ORDERS(sb));
> > +
> >
> >       spin_lock_init(&sbi->s_md_lock);
> >       sbi->s_mb_free_pending = 0;
> > diff --git a/fs/ext4/mballoc.h b/fs/ext4/mballoc.h
> > index 7597330dbdf8..02861406932f 100644
> > --- a/fs/ext4/mballoc.h
> > +++ b/fs/ext4/mballoc.h
> > @@ -78,6 +78,11 @@
> >  */
> > #define MB_DEFAULT_MAX_INODE_PREALLOC 512
> >
> > +/*
> > + * Number of valid buddy orders
> > + */
> > +#define MB_NUM_ORDERS(sb)            ((sb)->s_blocksize_bits + 2)
> > +
> > struct ext4_free_data {
> >       /* this links the free block information from sb_info */
> >       struct list_head                efd_list;
> > --
> > 2.30.0.478.g8a0d178c01-goog
> >
>

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