2023-03-11 09:06:53

by Kemeng Shi

Subject: [PATCH 2/2] ext4: avoid unnecessary pointer dereference in ext4_mb_normalize_request

Result of EXT4_SB(ac->ac_sb) is already stored in sbi at beginning of
ext4_mb_normalize_request. Use sbi instead of EXT4_SB(ac->ac_sb) to
remove unnecessary pointer dereference.

Signed-off-by: Kemeng Shi <[email protected]>
---
fs/ext4/mballoc.c | 8 +++-----
1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 13dce6f07fa4..d94eb52dda17 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -4049,7 +4049,7 @@ ext4_mb_normalize_request(struct ext4_allocation_context *ac,
size = 8 * 1024 * 1024;
} else {
start_off = (loff_t) ac->ac_o_ex.fe_logical << bsbits;
- size = (loff_t) EXT4_C2B(EXT4_SB(ac->ac_sb),
+ size = (loff_t) EXT4_C2B(sbi,
ac->ac_o_ex.fe_len) << bsbits;
}
size = size >> bsbits;
@@ -4094,8 +4094,7 @@ ext4_mb_normalize_request(struct ext4_allocation_context *ac,
continue;
}

- pa_end = pa->pa_lstart + EXT4_C2B(EXT4_SB(ac->ac_sb),
- pa->pa_len);
+ pa_end = pa->pa_lstart + EXT4_C2B(sbi, pa->pa_len);

/* PA must not overlap original request */
BUG_ON(!(ac->ac_o_ex.fe_logical >= pa_end ||
@@ -4128,8 +4127,7 @@ ext4_mb_normalize_request(struct ext4_allocation_context *ac,

spin_lock(&pa->pa_lock);
if (pa->pa_deleted == 0) {
- pa_end = pa->pa_lstart + EXT4_C2B(EXT4_SB(ac->ac_sb),
- pa->pa_len);
+ pa_end = pa->pa_lstart + EXT4_C2B(sbi, pa->pa_len);
BUG_ON(!(start >= pa_end || end <= pa->pa_lstart));
}
spin_unlock(&pa->pa_lock);
--
2.30.0

2023-03-13 02:13:53

by Ritesh Harjani

Subject: Re: [PATCH 2/2] ext4: avoid unnecessary pointer dereference in ext4_mb_normalize_request

Kemeng Shi <[email protected]> writes:

> Result of EXT4_SB(ac->ac_sb) is already stored in sbi at beginning of
> ext4_mb_normalize_request. Use sbi instead of EXT4_SB(ac->ac_sb) to
> remove unnecessary pointer dereference.
>
> Signed-off-by: Kemeng Shi <[email protected]>
> ---
> fs/ext4/mballoc.c | 8 +++-----
> 1 file changed, 3 insertions(+), 5 deletions(-)
>

Looks good to me. Please feel free to add -

Reviewed-by: Ritesh Harjani (IBM) <[email protected]>


> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
> index 13dce6f07fa4..d94eb52dda17 100644
> --- a/fs/ext4/mballoc.c
> +++ b/fs/ext4/mballoc.c
> @@ -4049,7 +4049,7 @@ ext4_mb_normalize_request(struct ext4_allocation_context *ac,
> size = 8 * 1024 * 1024;
> } else {
> start_off = (loff_t) ac->ac_o_ex.fe_logical << bsbits;
> - size = (loff_t) EXT4_C2B(EXT4_SB(ac->ac_sb),
> + size = (loff_t) EXT4_C2B(sbi,
> ac->ac_o_ex.fe_len) << bsbits;
> }
> size = size >> bsbits;
> @@ -4094,8 +4094,7 @@ ext4_mb_normalize_request(struct ext4_allocation_context *ac,
> continue;
> }
>
> - pa_end = pa->pa_lstart + EXT4_C2B(EXT4_SB(ac->ac_sb),
> - pa->pa_len);
> + pa_end = pa->pa_lstart + EXT4_C2B(sbi, pa->pa_len);
>
> /* PA must not overlap original request */
> BUG_ON(!(ac->ac_o_ex.fe_logical >= pa_end ||
> @@ -4128,8 +4127,7 @@ ext4_mb_normalize_request(struct ext4_allocation_context *ac,
>
> spin_lock(&pa->pa_lock);
> if (pa->pa_deleted == 0) {
> - pa_end = pa->pa_lstart + EXT4_C2B(EXT4_SB(ac->ac_sb),
> - pa->pa_len);
> + pa_end = pa->pa_lstart + EXT4_C2B(sbi, pa->pa_len);
> BUG_ON(!(start >= pa_end || end <= pa->pa_lstart));
> }
> spin_unlock(&pa->pa_lock);
> --
> 2.30.0