[PATCH v2 0/3] Replace opencoded set_mask_bits

[PATCH v2 0/3] Replace opencoded set_mask_bits

[Vineet Gupta]

Hi,

Repost of [1] rebased on 5.0-rc3 + accumulated Acked-by/Reviewed-by.
No code changes since v1.

Please consider applying.

[1] http://lists.infradead.org/pipermail/linux-snps-arc/2019-January/005201.html

Thx,
-Vineet

Vineet Gupta (3):
  coredump: Replace opencoded set_mask_bits()
  fs: inode_set_flags() replace opencoded set_mask_bits()
  bitops.h: set_mask_bits() to return old value

 fs/exec.c              | 7 +------
 fs/inode.c             | 8 +-------
 include/linux/bitops.h | 2 +-
 3 files changed, 3 insertions(+), 14 deletions(-)

-- 
2.7.4

[PATCH v2 1/3] coredump: Replace opencoded set_mask_bits()

[Vineet Gupta]

Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: linux-fsdevel@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Link: http://lkml.kernel.org/g/20150807115710.GA16897@redhat.com
Reviewed-by: Anthony Yznaga <anthony.yznaga@oracle.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
---
 fs/exec.c | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/fs/exec.c b/fs/exec.c
index fb72d36f7823..df7f05362283 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1944,15 +1944,10 @@ EXPORT_SYMBOL(set_binfmt);
  */
 void set_dumpable(struct mm_struct *mm, int value)
 {
-	unsigned long old, new;
-
 	if (WARN_ON((unsigned)value > SUID_DUMP_ROOT))
 		return;
 
-	do {
-		old = READ_ONCE(mm->flags);
-		new = (old & ~MMF_DUMPABLE_MASK) | value;
-	} while (cmpxchg(&mm->flags, old, new) != old);
+	set_mask_bits(&mm->flags, MMF_DUMPABLE_MASK, value);
 }
 
 SYSCALL_DEFINE3(execve,
-- 
2.7.4

[PATCH v2 2/3] fs: inode_set_flags() replace opencoded set_mask_bits()

[Vineet Gupta]

It seems that 5f16f3225b0624 and 00a1a053ebe5, both with same commitlog
("ext4: atomically set inode->i_flags in ext4_set_inode_flags()")
introduced the set_mask_bits API, but somehow missed not using it in
ext4 in the end

Also, set_mask_bits is used in fs quite a bit and we can possibly come up
with a generic llsc based implementation (w/o the cmpxchg loop)

Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: linux-fsdevel@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Reviewed-by: Anthony Yznaga <anthony.yznaga@oracle.com>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
---
 fs/inode.c | 8 +-------
 1 file changed, 1 insertion(+), 7 deletions(-)

diff --git a/fs/inode.c b/fs/inode.c
index 0cd47fe0dbe5..799b0c4beda8 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -2096,14 +2096,8 @@ EXPORT_SYMBOL(inode_dio_wait);
 void inode_set_flags(struct inode *inode, unsigned int flags,
 		     unsigned int mask)
 {
-	unsigned int old_flags, new_flags;
-
 	WARN_ON_ONCE(flags & ~mask);
-	do {
-		old_flags = READ_ONCE(inode->i_flags);
-		new_flags = (old_flags & ~mask) | flags;
-	} while (unlikely(cmpxchg(&inode->i_flags, old_flags,
-				  new_flags) != old_flags));
+	set_mask_bits(&inode->i_flags, mask, flags);
 }
 EXPORT_SYMBOL(inode_set_flags);
 
-- 
2.7.4

[PATCH v2 3/3] bitops.h: set_mask_bits() to return old value

[Vineet Gupta]

| > Also, set_mask_bits is used in fs quite a bit and we can possibly come up
| > with a generic llsc based implementation (w/o the cmpxchg loop)
|
| May I also suggest changing the return value of set_mask_bits() to old.
|
| You can compute the new value given old, but you cannot compute the old
| value given new, therefore old is the better return value. Also, no
| current user seems to use the return value, so changing it is without
| risk.

Link: http://lkml.kernel.org/g/20150807110955.GH16853@twins.programming.kicks-ass.net
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Cc: Miklos Szeredi <mszeredi@redhat.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Anthony Yznaga <anthony.yznaga@oracle.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
---
 include/linux/bitops.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/bitops.h b/include/linux/bitops.h
index 705f7c442691..602af23b98c7 100644
--- a/include/linux/bitops.h
+++ b/include/linux/bitops.h
@@ -246,7 +246,7 @@ static __always_inline void __assign_bit(long nr, volatile unsigned long *addr,
 		new__ = (old__ & ~mask__) | bits__;		\
 	} while (cmpxchg(ptr, old__, new__) != old__);		\
 								\
-	new__;							\
+	old__;							\
 })
 #endif
 
-- 
2.7.4

Re: [PATCH v2 0/3] Replace opencoded set_mask_bits

[Vineet Gupta]

On 1/23/19 12:33 PM, Vineet Gupta wrote:
> Hi,
> 
> Repost of [1] rebased on 5.0-rc3 + accumulated Acked-by/Reviewed-by.
> No code changes since v1.
> 
> Please consider applying.
> 
> [1] http://lists.infradead.org/pipermail/linux-snps-arc/2019-January/005201.html
> 
> Thx,
> -Vineet

Ping ! @Peter, @Arnd are you happy with this. If so, Andrew can you please add
this via mm tree or do i need to pester the respective maintainers !

Thx,
-Vineet

> 
> Vineet Gupta (3):
>   coredump: Replace opencoded set_mask_bits()
>   fs: inode_set_flags() replace opencoded set_mask_bits()
>   bitops.h: set_mask_bits() to return old value
> 
>  fs/exec.c              | 7 +------
>  fs/inode.c             | 8 +-------
>  include/linux/bitops.h | 2 +-
>  3 files changed, 3 insertions(+), 14 deletions(-)
>