f2fs: modify the readahead method in ra_node_page()

ra_node_page() is used to read ahead one node page. Comparing to regular
read, it's faster because it doesn't wait for IO completion.
But if it is called twice for reading the same block, and the IO request
from the first call hasn't been completed before the second call, the second
call will have to wait until the read is over.

Here use the code in __do_page_cache_readahead() to solve this problem.
It does nothing when someone else already puts the page in mapping. The
status of page should be assured by whoever puts it there.
This implement also prevents alteration of page reference count.

Signed-off-by: Fan li <fanofcode.li@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
index d714b607bf468bca43f9e3423b7cbc40c3400d84..7b805f7f63409bbbc2ef9be01bb4988f9d034eb2 100644 (file)
--- a/fs/f2fs/node.c
+++ b/fs/f2fs/node.c
@@ -1084,12 +1084,11 @@ void ra_node_page(struct f2fs_sb_info *sbi, nid_t nid)
                return;
        f2fs_bug_on(sbi, check_nid_range(sbi, nid));
 
-       apage = find_get_page(NODE_MAPPING(sbi), nid);
-       if (apage && PageUptodate(apage)) {
-               f2fs_put_page(apage, 0);
+       rcu_read_lock();
+       apage = radix_tree_lookup(&NODE_MAPPING(sbi)->page_tree, nid);
+       rcu_read_unlock();
+       if (apage)
                return;
-       }
-       f2fs_put_page(apage, 0);
 
        apage = grab_cache_page(NODE_MAPPING(sbi), nid);
        if (!apage)