On Tue, May 27, 2014 at 9:28 PM, Hugh Dickins <hughd@xxxxxxxxxx> wrote:
>> Signed-off-by: J. R. Okajima <hooanon05g@xxxxxxxxx>
>
> Reviewed-by: Jan Kara <jack@xxxxxxx>
> Acked-by: Hugh Dickins <hughd@xxxxxxxxxx>
>
>> ---
>> fs/inode.c | 6 +++++-
>> 1 file changed, 5 insertions(+), 1 deletion(-)
>>
>> diff --git a/fs/inode.c b/fs/inode.c
>> index f96d2a6..a3e274a 100644
>> --- a/fs/inode.c
>> +++ b/fs/inode.c
>> @@ -848,7 +848,11 @@ unsigned int get_next_ino(void)
>> }
>> #endif
>>
>> - *p = ++res;
>> + res++;
>> + /* never zero */
>> + if (unlikely(!res))
>> + res++;
>> + *p = res;
>> put_cpu_var(last_ino);
>> return res;
>> }
This is not right.
Each cpu 'owns' a window of 1024 consecutive inums.
If res == 0, then 1 does not necessarily belong to this cpu, and you
risk that about 1024 duplicate inums are given.
You need something like (sorry for bad formatting)
diff --git a/fs/inode.c b/fs/inode.c
index f96d2a6f88cc..66fd1189ddaa 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -839,6 +839,8 @@ unsigned int get_next_ino(void)
unsigned int *p = &get_cpu_var(last_ino);
unsigned int res = *p;
+start:
+
#ifdef CONFIG_SMP
if (unlikely((res & (LAST_INO_BATCH-1)) == 0)) {
static atomic_t shared_last_ino;
@@ -848,7 +850,10 @@ unsigned int get_next_ino(void)
}
#endif
- *p = ++res;
+ if (unlikely(++res == 0))
+ goto start;
+ *p = res;
+
put_cpu_var(last_ino);
return res;
}
--
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