On 07/18/2010 08:57 AM, Wang Sheng-Hui wrote:
> Sorry to resend this patch. For the 2nd patch should
> be applied after this patch, I just send them together.
>
> Following is the explanation of the patch:
> The comment for struct shrinker in include/linux/mm.h says
> "shrink...It should return the number of objects which remain in the
> cache."
> Please notice the word "remain".
>
> In fs/mbcache.h, mb_cache_shrink_fn is used as the shrink function:
> static struct shrinker mb_cache_shrinker = {
> .shrink = mb_cache_shrink_fn,
> .seeks = DEFAULT_SEEKS,
> };
> In mb_cache_shrink_fn, the return value for nr_to_scan > 0 is the
> number of mb_cache_entry before shrink operation. It may because the
> memory usage for mbcache is low, so the effect is not so obvious.
>
> Per Eric Sandeen, we should do the counting only once.
> Per Christoph Hellwig, we should use list_for_each_entry instead of
> list_for_each here.
>
> Following patch is against 2.6.35-rc4. Please check it.
>
>
> Signed-off-by: Wang Sheng-Hui <crosslonelyover@xxxxxxxxx>
Reviewed-by: Eric Sandeen <sandeen@xxxxxxxxxx>
Thanks,
-Eric
> ---
> fs/mbcache.c | 22 +++++++++++-----------
> 1 files changed, 11 insertions(+), 11 deletions(-)
>
> diff --git a/fs/mbcache.c b/fs/mbcache.c
> index ec88ff3..5697d9e 100644
> --- a/fs/mbcache.c
> +++ b/fs/mbcache.c
> @@ -201,21 +201,13 @@ mb_cache_shrink_fn(int nr_to_scan, gfp_t gfp_mask)
> {
> LIST_HEAD(free_list);
> struct list_head *l, *ltmp;
> + struct mb_cache *cache;
> int count = 0;
>
> - spin_lock(&mb_cache_spinlock);
> - list_for_each(l, &mb_cache_list) {
> - struct mb_cache *cache =
> - list_entry(l, struct mb_cache, c_cache_list);
> - mb_debug("cache %s (%d)", cache->c_name,
> - atomic_read(&cache->c_entry_count));
> - count += atomic_read(&cache->c_entry_count);
> - }
> mb_debug("trying to free %d entries", nr_to_scan);
> - if (nr_to_scan == 0) {
> - spin_unlock(&mb_cache_spinlock);
> + if (nr_to_scan == 0)
> goto out;
> - }
> +
> while (nr_to_scan-- && !list_empty(&mb_cache_lru_list)) {
> struct mb_cache_entry *ce =
> list_entry(mb_cache_lru_list.next,
> @@ -229,6 +221,14 @@ mb_cache_shrink_fn(int nr_to_scan, gfp_t gfp_mask)
> e_lru_list), gfp_mask);
> }
> out:
> + spin_lock(&mb_cache_spinlock);
> + list_for_each_entry(cache, &mb_cache_list, c_cache_list) {
> + mb_debug("cache %s (%d)", cache->c_name,
> + atomic_read(&cache->c_entry_count));
> + count += atomic_read(&cache->c_entry_count);
> + }
> + spin_unlock(&mb_cache_spinlock);
> +
> return (count / 100) * sysctl_vfs_cache_pressure;
> }
>
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