Patchwork [1/1] ext4: use proper little-endian bitops

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Submitter Andrew Morton
Date Nov. 15, 2011, 10:56 p.m.
Message ID <201111152256.pAFMu6Xw017147@wpaz9.hot.corp.google.com>
Download mbox | patch
Permalink /patch/125881/
State Accepted
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Comments

Andrew Morton - Nov. 15, 2011, 10:56 p.m.
From: Akinobu Mita <akinobu.mita@gmail.com>
Subject: ext4: use proper little-endian bitops

ext4_{set,clear}_bit() is defined as __test_and_{set,clear}_bit_le() for
ext4.  Only two ext4_{set,clear}_bit() calls check the return value.  The
rest of calls ignore the return value and they can be replaced with
__{set,clear}_bit_le().

This changes ext4_{set,clear}_bit() from __test_and_{set,clear}_bit_le()
to __{set,clear}_bit_le() and introduces ext4_test_and_{set,clear}_bit()
for the two places where old bit needs to be returned.

This ext4_{set,clear}_bit() change is considered safe, because if someone
uses these macros without noticing the change, new ext4_{set,clear}_bit
don't have return value and causes compiler errors where the return value
is used.

This also removes unused ext4_find_first_zero_bit().

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Cc: Andreas Dilger <adilger.kernel@dilger.ca>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 fs/ext4/ext4.h   |    7 ++++---
 fs/ext4/ialloc.c |    4 ++--
 2 files changed, 6 insertions(+), 5 deletions(-)
Theodore Ts'o - Dec. 29, 2011, 1:34 a.m.
On Tue, Nov 15, 2011 at 02:56:06PM -0800, akpm@linux-foundation.org wrote:
> From: Akinobu Mita <akinobu.mita@gmail.com>
> Subject: ext4: use proper little-endian bitops
> 
> ext4_{set,clear}_bit() is defined as __test_and_{set,clear}_bit_le() for
> ext4.  Only two ext4_{set,clear}_bit() calls check the return value.  The
> rest of calls ignore the return value and they can be replaced with
> __{set,clear}_bit_le().
> 
> This changes ext4_{set,clear}_bit() from __test_and_{set,clear}_bit_le()
> to __{set,clear}_bit_le() and introduces ext4_test_and_{set,clear}_bit()
> for the two places where old bit needs to be returned.
> 
> This ext4_{set,clear}_bit() change is considered safe, because if someone
> uses these macros without noticing the change, new ext4_{set,clear}_bit
> don't have return value and causes compiler errors where the return value
> is used.
> 
> This also removes unused ext4_find_first_zero_bit().
> 
> Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
> Cc: "Theodore Ts'o" <tytso@mit.edu>
> Cc: Andreas Dilger <adilger.kernel@dilger.ca>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Applied.

						- Ted
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Patch

diff -puN fs/ext4/ext4.h~ext4-use-proper-little-endian-bitops fs/ext4/ext4.h
--- a/fs/ext4/ext4.h~ext4-use-proper-little-endian-bitops
+++ a/fs/ext4/ext4.h
@@ -957,12 +957,13 @@  struct ext4_inode_info {
 #define test_opt2(sb, opt)		(EXT4_SB(sb)->s_mount_opt2 & \
 					 EXT4_MOUNT2_##opt)
 
-#define ext4_set_bit			__test_and_set_bit_le
+#define ext4_test_and_set_bit		__test_and_set_bit_le
+#define ext4_set_bit			__set_bit_le
 #define ext4_set_bit_atomic		ext2_set_bit_atomic
-#define ext4_clear_bit			__test_and_clear_bit_le
+#define ext4_test_and_clear_bit		__test_and_clear_bit_le
+#define ext4_clear_bit			__clear_bit_le
 #define ext4_clear_bit_atomic		ext2_clear_bit_atomic
 #define ext4_test_bit			test_bit_le
-#define ext4_find_first_zero_bit	find_first_zero_bit_le
 #define ext4_find_next_zero_bit		find_next_zero_bit_le
 #define ext4_find_next_bit		find_next_bit_le
 
diff -puN fs/ext4/ialloc.c~ext4-use-proper-little-endian-bitops fs/ext4/ialloc.c
--- a/fs/ext4/ialloc.c~ext4-use-proper-little-endian-bitops
+++ a/fs/ext4/ialloc.c
@@ -252,7 +252,7 @@  void ext4_free_inode(handle_t *handle, s
 		fatal = ext4_journal_get_write_access(handle, bh2);
 	}
 	ext4_lock_group(sb, block_group);
-	cleared = ext4_clear_bit(bit, bitmap_bh->b_data);
+	cleared = ext4_test_and_clear_bit(bit, bitmap_bh->b_data);
 	if (fatal || !cleared) {
 		ext4_unlock_group(sb, block_group);
 		goto out;
@@ -618,7 +618,7 @@  static int ext4_claim_inode(struct super
 	 */
 	down_read(&grp->alloc_sem);
 	ext4_lock_group(sb, group);
-	if (ext4_set_bit(ino, inode_bitmap_bh->b_data)) {
+	if (ext4_test_and_set_bit(ino, inode_bitmap_bh->b_data)) {
 		/* not a free inode */
 		retval = 1;
 		goto err_ret;