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SubjectRe: [PATCH] VFS: Go through the LRU list of inode from head

Quoting Jan Kara <jack@suse.cz>:

> On Thu 21-06-12 17:00:27, Cong Meng wrote:
>> Go through the LRU list of inode from head.
>>
>> (I'm not sure whether there is any trick here I doesn't get. If yes,
>> any one could explain it)
> Look at inode_lru_list_add(). It adds at the head of the list. So you
> should take from the tail to get the least recently used element...

I still have a quetion about the subsequent code and comment:

inode = list_entry(sb->s_inode_lru.prev, struct inode, i_lru);
/*
* we are inverting the sb->s_inode_lru_lock/inode->i_lock here,
* so use a trylock. If we fail to get the lock, just move the
* inode to the back of the list so we don't spin on it.
*/
if (!spin_trylock(&inode->i_lock)) {
list_move_tail(&inode->i_lru, &sb->s_inode_lru);
continue;
}

Shouldn't the inode be moved to the head to avoid spin on it?
I note that list_move was replaced by list_move_tail purposely in a commit.


and below piece of code (at the bottom of prune_icache_sb()):

if (inode != list_entry(sb->s_inode_lru.next,
struct inode, i_lru))
continue; /* wrong inode or list_empty */

Should the inode be compared against to the tail of the list other
than the head
after re-get the lru lock?

thanks.
cong.
>
> Honza
>
>>
>> Signed-off-by: Cong Meng <mc@linux.vnet.ibm.com>
>> ---
>> fs/inode.c | 2 +-
>> 1 files changed, 1 insertions(+), 1 deletions(-)
>>
>> diff --git a/fs/inode.c b/fs/inode.c
>> index 775cbab..aac8449 100644
>> --- a/fs/inode.c
>> +++ b/fs/inode.c
>> @@ -704,7 +704,7 @@ void prune_icache_sb(struct super_block *sb,
>> int nr_to_scan)
>> if (list_empty(&sb->s_inode_lru))
>> break;
>>
>> - inode = list_entry(sb->s_inode_lru.prev, struct inode, i_lru);
>> + inode = list_entry(sb->s_inode_lru.next, struct inode, i_lru);
>>
>> /*
>> * we are inverting the sb->s_inode_lru_lock/inode->i_lock here,
>> --
>> 1.7.5.4
>>
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at http://vger.kernel.org/majordomo-info.html
> --
> Jan Kara <jack@suse.cz>
> SUSE Labs, CR





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