Re: [PATCH v2] mm/shmem.c: make shmem_mapping() inline
On Sat, Nov 14, 2020 at 10:50:39AM -0800, Andrew Morton wrote:
> On Sat, 14 Nov 2020 13:51:34 +0800 Hui Su wrote:
>
> > inline the shmem_mapping(), and use shmem_mapping()
> > instead of 'inode->i_mapping->a_ops == _aops'
> > in shmem_evict_inode().
> >
> > ...
> >
> > --- a/mm/shmem.c
> > +++ b/mm/shmem.c
> > @@ -1152,7 +1152,7 @@ static void shmem_evict_inode(struct inode *inode)
> > struct shmem_inode_info *info = SHMEM_I(inode);
> > struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
> >
> > - if (inode->i_mapping->a_ops == _aops) {
> > + if (shmem_mapping(inode->i_mapping)) {
> > shmem_unacct_size(info->flags, inode->i_size);
> > inode->i_size = 0;
> > shmem_truncate_range(inode, 0, (loff_t)-1);
> > @@ -2352,7 +2352,7 @@ static struct inode *shmem_get_inode(struct
> > super_block *sb, const struct inode
> > return inode;
> > }
> >
> > -bool shmem_mapping(struct address_space *mapping)
> > +inline bool shmem_mapping(struct address_space *mapping)
> > {
> > return mapping->a_ops == _aops;
> > }
>
> huh. I'd have expected the inlining in shmem_evict_inode() to not work
> because the compiler hasn't seen the definition yet. But gcc has
> evidently become smarter about that.
>
> But really, shmem_mapping() isn't worth an out-of-line call from any
> callsite - it would be best to make it inlined everywhere.
>
> - make shmem_aops global
> - declare shmem_aops in shmem_fs.h
> - export shmem_aops to modules for drivers/dma-buf/udmabuf.c
> - include linux/fs.h in shmem_fs.h for address_space_operations (we already
> include fs.h via swap.h, but we shouldn't depend on that)
> - make shmem_mapping() a static inline in shmem_fs.h.
Yeah, thanks.
i will resend a PATCH V3 later.
Re: [PATCH v2] mm/shmem.c: make shmem_mapping() inline
On Sat, Nov 14, 2020 at 10:50:39AM -0800, Andrew Morton wrote: > But really, shmem_mapping() isn't worth an out-of-line call from any > callsite - it would be best to make it inlined everywhere. > > - make shmem_aops global > - declare shmem_aops in shmem_fs.h > - export shmem_aops to modules for drivers/dma-buf/udmabuf.c > - include linux/fs.h in shmem_fs.h for address_space_operations (we already > include fs.h via swap.h, but we shouldn't depend on that) > - make shmem_mapping() a static inline in shmem_fs.h. ... or use an AS_ bit to make shmem_mapping() global inline without exposing the shmem_aops symbol. We're not short of AS_ bits, and it's probably even cheaper than a pointer comparison. A really good changelog would explain why we need shmem_mapping() everywhere that we currently use it. It's not immediately obvious why so many places need to know.
Re: [PATCH v2] mm/shmem.c: make shmem_mapping() inline
On Sat, 14 Nov 2020 13:51:34 +0800 Hui Su wrote:
> inline the shmem_mapping(), and use shmem_mapping()
> instead of 'inode->i_mapping->a_ops == _aops'
> in shmem_evict_inode().
>
> ...
>
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -1152,7 +1152,7 @@ static void shmem_evict_inode(struct inode *inode)
> struct shmem_inode_info *info = SHMEM_I(inode);
> struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
>
> - if (inode->i_mapping->a_ops == _aops) {
> + if (shmem_mapping(inode->i_mapping)) {
> shmem_unacct_size(info->flags, inode->i_size);
> inode->i_size = 0;
> shmem_truncate_range(inode, 0, (loff_t)-1);
> @@ -2352,7 +2352,7 @@ static struct inode *shmem_get_inode(struct super_block
> *sb, const struct inode
> return inode;
> }
>
> -bool shmem_mapping(struct address_space *mapping)
> +inline bool shmem_mapping(struct address_space *mapping)
> {
> return mapping->a_ops == _aops;
> }
huh. I'd have expected the inlining in shmem_evict_inode() to not work
because the compiler hasn't seen the definition yet. But gcc has
evidently become smarter about that.
But really, shmem_mapping() isn't worth an out-of-line call from any
callsite - it would be best to make it inlined everywhere.
- make shmem_aops global
- declare shmem_aops in shmem_fs.h
- export shmem_aops to modules for drivers/dma-buf/udmabuf.c
- include linux/fs.h in shmem_fs.h for address_space_operations (we already
include fs.h via swap.h, but we shouldn't depend on that)
- make shmem_mapping() a static inline in shmem_fs.h.
[PATCH v2] mm/shmem.c: make shmem_mapping() inline
inline the shmem_mapping(), and use shmem_mapping()
instead of 'inode->i_mapping->a_ops == _aops'
in shmem_evict_inode().
v1->v2:
remove the inline for func declaration in shmem_fs.h
Reviewed-by: Pankaj Gupta
Reported-by: kernel test robot
Signed-off-by: Hui Su
---
mm/shmem.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/mm/shmem.c b/mm/shmem.c
index 537c137698f8..7395d8e8226a 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1152,7 +1152,7 @@ static void shmem_evict_inode(struct inode *inode)
struct shmem_inode_info *info = SHMEM_I(inode);
struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
- if (inode->i_mapping->a_ops == _aops) {
+ if (shmem_mapping(inode->i_mapping)) {
shmem_unacct_size(info->flags, inode->i_size);
inode->i_size = 0;
shmem_truncate_range(inode, 0, (loff_t)-1);
@@ -2352,7 +2352,7 @@ static struct inode *shmem_get_inode(struct super_block
*sb, const struct inode
return inode;
}
-bool shmem_mapping(struct address_space *mapping)
+inline bool shmem_mapping(struct address_space *mapping)
{
return mapping->a_ops == _aops;
}
--
2.29.0
