* [PATCH 1/1 linux-next] fs/ufs/super.c: remove CONFIG_SMP/CONFIG_PREEMPT testing
@ 2015-02-01 11:36 Fabian Frederick
2015-02-02 23:52 ` Andrew Morton
0 siblings, 1 reply; 2+ messages in thread
From: Fabian Frederick @ 2015-02-01 11:36 UTC (permalink / raw)
To: linux-kernel; +Cc: Fabian Frederick, Evgeniy Dushistov, Andrew Morton
Let locking subsystem decide on mutex management.
Cc: Evgeniy Dushistov <dushistov@mail.ru>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Fabian Frederick <fabf@skynet.be>
---
fs/ufs/super.c | 4 ----
1 file changed, 4 deletions(-)
diff --git a/fs/ufs/super.c b/fs/ufs/super.c
index e515e99..8092d37 100644
--- a/fs/ufs/super.c
+++ b/fs/ufs/super.c
@@ -95,22 +95,18 @@
void lock_ufs(struct super_block *sb)
{
-#if defined(CONFIG_SMP) || defined (CONFIG_PREEMPT)
struct ufs_sb_info *sbi = UFS_SB(sb);
mutex_lock(&sbi->mutex);
sbi->mutex_owner = current;
-#endif
}
void unlock_ufs(struct super_block *sb)
{
-#if defined(CONFIG_SMP) || defined (CONFIG_PREEMPT)
struct ufs_sb_info *sbi = UFS_SB(sb);
sbi->mutex_owner = NULL;
mutex_unlock(&sbi->mutex);
-#endif
}
static struct inode *ufs_nfs_get_inode(struct super_block *sb, u64 ino, u32 generation)
--
2.1.0
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH 1/1 linux-next] fs/ufs/super.c: remove CONFIG_SMP/CONFIG_PREEMPT testing
2015-02-01 11:36 [PATCH 1/1 linux-next] fs/ufs/super.c: remove CONFIG_SMP/CONFIG_PREEMPT testing Fabian Frederick
@ 2015-02-02 23:52 ` Andrew Morton
0 siblings, 0 replies; 2+ messages in thread
From: Andrew Morton @ 2015-02-02 23:52 UTC (permalink / raw)
To: Fabian Frederick; +Cc: linux-kernel, Evgeniy Dushistov
On Sun, 1 Feb 2015 12:36:57 +0100 Fabian Frederick <fabf@skynet.be> wrote:
> Let locking subsystem decide on mutex management.
>
> ...
>
> --- a/fs/ufs/super.c
> +++ b/fs/ufs/super.c
> @@ -95,22 +95,18 @@
>
> void lock_ufs(struct super_block *sb)
> {
> -#if defined(CONFIG_SMP) || defined (CONFIG_PREEMPT)
> struct ufs_sb_info *sbi = UFS_SB(sb);
>
> mutex_lock(&sbi->mutex);
> sbi->mutex_owner = current;
> -#endif
> }
Good heavens.
This patch is a bugfix. lock_ufs() is assuming that on non-preempt
uniprocessor, the calling code will run atomically up to the matching
unlock_ufs().
But that isn't true. The very first site I looked at (ufs_frag_map)
does sb_bread() under lock_ufs(. And sb_bread() will call schedule(),
very commonly.
The ->mutex_owner stuff is a bit hacky but should work OK.
Care to resend the patch with a more alarming changelog?
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