f2fs: reduce unncessary locking pages during read
This patch reduces redundant locking and unlocking pages during read operations.
In f2fs_readpage, let's use wait_on_page_locked() instead of lock_page.
And then, when we need to modify any data finally, let's lock the page so that
we can avoid lock contention.
[readpage rule]
- The f2fs_readpage returns unlocked page, or released page too in error cases.
- Its caller should handle read error, -EIO, after locking the page, which
indicates read completion.
- Its caller should check PageUptodate after grab_cache_page.
Signed-off-by: Changman Lee <cm224.lee@samsung.com>
Reviewed-by: Namjae Jeon <namjae.jeon@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>
diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 277966a..c8e20b6 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -199,12 +199,17 @@
if (!page)
return ERR_PTR(-ENOMEM);
- err = f2fs_readpage(sbi, page, dn.data_blkaddr, READ_SYNC);
- if (err) {
- f2fs_put_page(page, 1);
- return ERR_PTR(err);
+ if (PageUptodate(page)) {
+ unlock_page(page);
+ return page;
}
- unlock_page(page);
+
+ err = f2fs_readpage(sbi, page, dn.data_blkaddr, READ_SYNC);
+ wait_on_page_locked(page);
+ if (!PageUptodate(page)) {
+ f2fs_put_page(page, 0);
+ return ERR_PTR(-EIO);
+ }
return page;
}
@@ -241,9 +246,13 @@
BUG_ON(dn.data_blkaddr == NULL_ADDR);
err = f2fs_readpage(sbi, page, dn.data_blkaddr, READ_SYNC);
- if (err) {
- f2fs_put_page(page, 1);
+ if (err)
return ERR_PTR(err);
+
+ lock_page(page);
+ if (!PageUptodate(page)) {
+ f2fs_put_page(page, 1);
+ return ERR_PTR(-EIO);
}
return page;
}
@@ -283,14 +292,17 @@
if (dn.data_blkaddr == NEW_ADDR) {
zero_user_segment(page, 0, PAGE_CACHE_SIZE);
+ SetPageUptodate(page);
} else {
err = f2fs_readpage(sbi, page, dn.data_blkaddr, READ_SYNC);
- if (err) {
- f2fs_put_page(page, 1);
+ if (err)
return ERR_PTR(err);
+ lock_page(page);
+ if (!PageUptodate(page)) {
+ f2fs_put_page(page, 1);
+ return ERR_PTR(-EIO);
}
}
- SetPageUptodate(page);
if (new_i_size &&
i_size_read(inode) < ((index + 1) << PAGE_CACHE_SHIFT)) {
@@ -325,22 +337,14 @@
/*
* Fill the locked page with data located in the block address.
- * Read operation is synchronous, and caller must unlock the page.
+ * Return unlocked page.
*/
int f2fs_readpage(struct f2fs_sb_info *sbi, struct page *page,
block_t blk_addr, int type)
{
struct block_device *bdev = sbi->sb->s_bdev;
- bool sync = (type == READ_SYNC);
struct bio *bio;
- /* This page can be already read by other threads */
- if (PageUptodate(page)) {
- if (!sync)
- unlock_page(page);
- return 0;
- }
-
down_read(&sbi->bio_sem);
/* Allocate a new bio */
@@ -354,18 +358,12 @@
kfree(bio->bi_private);
bio_put(bio);
up_read(&sbi->bio_sem);
+ f2fs_put_page(page, 1);
return -EFAULT;
}
submit_bio(type, bio);
up_read(&sbi->bio_sem);
-
- /* wait for read completion if sync */
- if (sync) {
- lock_page(page);
- if (PageError(page))
- return -EIO;
- }
return 0;
}
@@ -636,18 +634,22 @@
/* Reading beyond i_size is simple: memset to zero */
zero_user_segments(page, 0, start, end, PAGE_CACHE_SIZE);
- return 0;
+ goto out;
}
if (dn.data_blkaddr == NEW_ADDR) {
zero_user_segment(page, 0, PAGE_CACHE_SIZE);
} else {
err = f2fs_readpage(sbi, page, dn.data_blkaddr, READ_SYNC);
- if (err) {
- f2fs_put_page(page, 1);
+ if (err)
return err;
+ lock_page(page);
+ if (!PageUptodate(page)) {
+ f2fs_put_page(page, 1);
+ return -EIO;
}
}
+out:
SetPageUptodate(page);
clear_cold_data(page);
return 0;