Message ID | 0c77de22-c0d0-4c1b-645a-865bcd2edc0a@gmail.com |
---|---|
State | Rejected |
Headers | show |
Series | [v2] ext4: delete invalid ac_b_extent backup inside ext4_mb_use_best_found() | expand |
On Aug 7, 2020, at 5:32 AM, brookxu <brookxu.cn@gmail.com> wrote: > > Delete invalid ac_b_extent backup inside ext4_mb_use_best_found(), > we have done this operation in ext4_mb_new_group_pa() and > ext4_mb_new_inode_pa(). I'm not sure I understand this patch completely. The calls to ext4_mb_new_group_pa() and ext4_mb_new_inode_pa() are done from ext4_mb_new_preallocation(), which is called at the *end* of ext4_mb_use_best_found() (i.e. after the lines that are being deleted). Maybe I'm confused by the description "we *have done* this operation" makes it seem like it was already done, but really it should be "we *will do* this operation in ..."? That said, it would make more sense to keep the one line here in ext4_mb_use_best_found() and remove the two duplicate lines in ext4_mb_new_group_pa() and ext4_mb_new_inode_pa()? In that case, the patch description would be more correct, like: Delete duplicate ac_b_extent backup in ext4_mb_new_group_pa() and ext4_mb_new_inode_pa(), since we have done this operation in ext4_mb_use_best_found() already. Cheers, Andreas PS: thank you for taking the time to look at this code and improve it. I know it is complex and hard to understand, but going through it like this and trimming off the bad bits makes it a bit easier to understand and maintain with each small patch. > Signed-off-by: Chunguang Xu <brookxu@tencent.com> > > diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c > index 9b1c3ad..fb63e9f 100644 > --- a/fs/ext4/mballoc.c > +++ b/fs/ext4/mballoc.c > @@ -1704,10 +1704,6 @@ static void ext4_mb_use_best_found(struct ext4_allocation_context *ac, > ac->ac_b_ex.fe_logical = ac->ac_g_ex.fe_logical; > ret = mb_mark_used(e4b, &ac->ac_b_ex); > > - /* preallocation can change ac_b_ex, thus we store actually > - * allocated blocks for history */ > - ac->ac_f_ex = ac->ac_b_ex; > - > ac->ac_status = AC_STATUS_FOUND; > ac->ac_tail = ret & 0xffff; > ac->ac_buddy = ret >> 16; > @@ -1726,8 +1722,8 @@ static void ext4_mb_use_best_found(struct ext4_allocation_context *ac, > /* store last allocated for subsequent stream allocation */ > if (ac->ac_flags & EXT4_MB_STREAM_ALLOC) { > spin_lock(&sbi->s_md_lock); > - sbi->s_mb_last_group = ac->ac_f_ex.fe_group; > - sbi->s_mb_last_start = ac->ac_f_ex.fe_start; > + sbi->s_mb_last_group = ac->ac_b_ex.fe_group; > + sbi->s_mb_last_start = ac->ac_b_ex.fe_start; > spin_unlock(&sbi->s_md_lock); > } > /* > -- > 1.8.3.1 Cheers, Andreas
Thank you very much for taking the time to review this patch. Due to poor thinking, there are some problems with this patch. I think this patch can be ignored. Thank you again for your time. thanks Andreas Dilger wrote on 2020/8/13 16:44: > On Aug 7, 2020, at 5:32 AM, brookxu <brookxu.cn@gmail.com> wrote: >> >> Delete invalid ac_b_extent backup inside ext4_mb_use_best_found(), >> we have done this operation in ext4_mb_new_group_pa() and >> ext4_mb_new_inode_pa(). > > I'm not sure I understand this patch completely. > > The calls to ext4_mb_new_group_pa() and ext4_mb_new_inode_pa() are > done from ext4_mb_new_preallocation(), which is called at the *end* > of ext4_mb_use_best_found() (i.e. after the lines that are being > deleted). > > Maybe I'm confused by the description "we *have done* this operation" > makes it seem like it was already done, but really it should be > "we *will do* this operation in ..."? > > That said, it would make more sense to keep the one line here in > ext4_mb_use_best_found() and remove the two duplicate lines in > ext4_mb_new_group_pa() and ext4_mb_new_inode_pa()? In that case, > the patch description would be more correct, like: > > Delete duplicate ac_b_extent backup in ext4_mb_new_group_pa() > and ext4_mb_new_inode_pa(), since we have done this operation > in ext4_mb_use_best_found() already. > > Cheers, Andreas > > PS: thank you for taking the time to look at this code and improve it. > I know it is complex and hard to understand, but going through it like > this and trimming off the bad bits makes it a bit easier to understand > and maintain with each small patch. > >> Signed-off-by: Chunguang Xu <brookxu@tencent.com> >> >> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c >> index 9b1c3ad..fb63e9f 100644 >> --- a/fs/ext4/mballoc.c >> +++ b/fs/ext4/mballoc.c >> @@ -1704,10 +1704,6 @@ static void ext4_mb_use_best_found(struct ext4_allocation_context *ac, >> ac->ac_b_ex.fe_logical = ac->ac_g_ex.fe_logical; >> ret = mb_mark_used(e4b, &ac->ac_b_ex); >> >> - /* preallocation can change ac_b_ex, thus we store actually >> - * allocated blocks for history */ >> - ac->ac_f_ex = ac->ac_b_ex; >> - >> ac->ac_status = AC_STATUS_FOUND; >> ac->ac_tail = ret & 0xffff; >> ac->ac_buddy = ret >> 16; >> @@ -1726,8 +1722,8 @@ static void ext4_mb_use_best_found(struct ext4_allocation_context *ac, >> /* store last allocated for subsequent stream allocation */ >> if (ac->ac_flags & EXT4_MB_STREAM_ALLOC) { >> spin_lock(&sbi->s_md_lock); >> - sbi->s_mb_last_group = ac->ac_f_ex.fe_group; >> - sbi->s_mb_last_start = ac->ac_f_ex.fe_start; >> + sbi->s_mb_last_group = ac->ac_b_ex.fe_group; >> + sbi->s_mb_last_start = ac->ac_b_ex.fe_start; >> spin_unlock(&sbi->s_md_lock); >> } >> /* >> -- >> 1.8.3.1 > > > Cheers, Andreas > > > > >
On 8/13/20 2:14 PM, Andreas Dilger wrote: > On Aug 7, 2020, at 5:32 AM, brookxu <brookxu.cn@gmail.com> wrote: >> >> Delete invalid ac_b_extent backup inside ext4_mb_use_best_found(), >> we have done this operation in ext4_mb_new_group_pa() and >> ext4_mb_new_inode_pa(). > > I'm not sure I understand this patch completely. > > The calls to ext4_mb_new_group_pa() and ext4_mb_new_inode_pa() are > done from ext4_mb_new_preallocation(), which is called at the *end* > of ext4_mb_use_best_found() (i.e. after the lines that are being > deleted). > > Maybe I'm confused by the description "we *have done* this operation" > makes it seem like it was already done, but really it should be > "we *will do* this operation in ..."? > > That said, it would make more sense to keep the one line here in > ext4_mb_use_best_found() and remove the two duplicate lines in > ext4_mb_new_group_pa() and ext4_mb_new_inode_pa()? In that case, > the patch description would be more correct, like: > > Delete duplicate ac_b_extent backup in ext4_mb_new_group_pa() > and ext4_mb_new_inode_pa(), since we have done this operation > in ext4_mb_use_best_found() already. > Looked into the mballoc code and I agree with Andreas points here. -ritesh
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c index 9b1c3ad..fb63e9f 100644 --- a/fs/ext4/mballoc.c +++ b/fs/ext4/mballoc.c @@ -1704,10 +1704,6 @@ static void ext4_mb_use_best_found(struct ext4_allocation_context *ac, ac->ac_b_ex.fe_logical = ac->ac_g_ex.fe_logical; ret = mb_mark_used(e4b, &ac->ac_b_ex); - /* preallocation can change ac_b_ex, thus we store actually - * allocated blocks for history */ - ac->ac_f_ex = ac->ac_b_ex; - ac->ac_status = AC_STATUS_FOUND; ac->ac_tail = ret & 0xffff; ac->ac_buddy = ret >> 16; @@ -1726,8 +1722,8 @@ static void ext4_mb_use_best_found(struct ext4_allocation_context *ac, /* store last allocated for subsequent stream allocation */ if (ac->ac_flags & EXT4_MB_STREAM_ALLOC) { spin_lock(&sbi->s_md_lock); - sbi->s_mb_last_group = ac->ac_f_ex.fe_group; - sbi->s_mb_last_start = ac->ac_f_ex.fe_start; + sbi->s_mb_last_group = ac->ac_b_ex.fe_group; + sbi->s_mb_last_start = ac->ac_b_ex.fe_start; spin_unlock(&sbi->s_md_lock); } /*
Delete invalid ac_b_extent backup inside ext4_mb_use_best_found(), we have done this operation in ext4_mb_new_group_pa() and ext4_mb_new_inode_pa(). Signed-off-by: Chunguang Xu <brookxu@tencent.com>