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/checkpoint.c b/fs/f2fs/checkpoint.c
index 2b6fc13..d947e66 100644 (file)
--- a/fs/f2fs/checkpoint.c
+++ b/fs/f2fs/checkpoint.c
@@ -57,13 +57,15 @@ repeat:
                cond_resched();
                goto repeat;
        }
-       if (f2fs_readpage(sbi, page, index, READ_SYNC)) {
-               f2fs_put_page(page, 1);
+       if (PageUptodate(page))
+               goto out;
+
+       if (f2fs_readpage(sbi, page, index, READ_SYNC))
                goto repeat;
-       }
-       mark_page_accessed(page);
 
-       /* We do not allow returning an errorneous page */
+       lock_page(page);
+out:
+       mark_page_accessed(page);
        return page;
 }
 

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 277966a..c8e20b6 100644 (file)
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -199,12 +199,17 @@ struct page *find_data_page(struct inode *inode, pgoff_t index)
        if (!page)
                return ERR_PTR(-ENOMEM);
 
+       if (PageUptodate(page)) {
+               unlock_page(page);
+               return page;
+       }
+
        err = f2fs_readpage(sbi, page, dn.data_blkaddr, READ_SYNC);
-       if (err) {
-               f2fs_put_page(page, 1);
-               return ERR_PTR(err);
+       wait_on_page_locked(page);
+       if (!PageUptodate(page)) {
+               f2fs_put_page(page, 0);
+               return ERR_PTR(-EIO);
        }
-       unlock_page(page);
        return page;
 }
 
@@ -241,9 +246,13 @@ struct page *get_lock_data_page(struct inode *inode, pgoff_t index)
        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 @@ struct page *get_new_data_page(struct inode *inode, pgoff_t index,
 
        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 @@ static void read_end_io(struct bio *bio, int err)
 
 /*
  * 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 @@ int f2fs_readpage(struct f2fs_sb_info *sbi, struct page *page,
                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 @@ static int f2fs_write_begin(struct file *file, struct address_space *mapping,
 
                /* 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;

diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
index a3cb1ff..9e6ed67 100644 (file)
--- a/fs/f2fs/node.c
+++ b/fs/f2fs/node.c
@@ -100,10 +100,13 @@ static void ra_nat_pages(struct f2fs_sb_info *sbi, int nid)
                page = grab_cache_page(mapping, index);
                if (!page)
                        continue;
-               if (f2fs_readpage(sbi, page, index, READ)) {
+               if (PageUptodate(page)) {
                        f2fs_put_page(page, 1);
                        continue;
                }
+               if (f2fs_readpage(sbi, page, index, READ))
+                       continue;
+
                f2fs_put_page(page, 0);
        }
 }
@@ -851,8 +854,16 @@ static int read_node_page(struct page *page, int type)
 
        get_node_info(sbi, page->index, &ni);
 
-       if (ni.blk_addr == NULL_ADDR)
+       if (ni.blk_addr == NULL_ADDR) {
+               f2fs_put_page(page, 1);
                return -ENOENT;
+       }
+
+       if (PageUptodate(page)) {
+               unlock_page(page);
+               return 0;
+       }
+
        return f2fs_readpage(sbi, page, ni.blk_addr, type);
 }
 
@@ -865,19 +876,18 @@ void ra_node_page(struct f2fs_sb_info *sbi, nid_t nid)
        struct page *apage;
 
        apage = find_get_page(mapping, nid);
-       if (apage && PageUptodate(apage))
-               goto release_out;
+       if (apage && PageUptodate(apage)) {
+               f2fs_put_page(apage, 0);
+               return;
+       }
        f2fs_put_page(apage, 0);
 
        apage = grab_cache_page(mapping, nid);
        if (!apage)
                return;
 
-       if (read_node_page(apage, READA))
-               unlock_page(apage);
-
-release_out:
-       f2fs_put_page(apage, 0);
+       if (read_node_page(apage, READA) == 0)
+               f2fs_put_page(apage, 0);
        return;
 }
 
@@ -892,11 +902,14 @@ struct page *get_node_page(struct f2fs_sb_info *sbi, pgoff_t nid)
                return ERR_PTR(-ENOMEM);
 
        err = read_node_page(page, 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);
+       }
        BUG_ON(nid != nid_of_node(page));
        mark_page_accessed(page);
        return page;
@@ -928,11 +941,8 @@ repeat:
                goto page_hit;
 
        err = read_node_page(page, READ_SYNC);
-       unlock_page(page);
-       if (err) {
-               f2fs_put_page(page, 0);
+       if (err)
                return ERR_PTR(err);
-       }
 
        /* Then, try readahead for siblings of the desired node */
        end = start + MAX_RA_NODE;
@@ -957,6 +967,7 @@ page_hit:
                f2fs_put_page(page, 1);
                goto repeat;
        }
+       mark_page_accessed(page);
        return page;
 }
 
@@ -1473,23 +1484,24 @@ int restore_node_summary(struct f2fs_sb_info *sbi,
        sum_entry = &sum->entries[0];
 
        for (i = 0; i < last_offset; i++, sum_entry++) {
+               /*
+                * In order to read next node page,
+                * we must clear PageUptodate flag.
+                */
+               ClearPageUptodate(page);
+
                if (f2fs_readpage(sbi, page, addr, READ_SYNC))
                        goto out;
 
+               lock_page(page);
                rn = (struct f2fs_node *)page_address(page);
                sum_entry->nid = rn->footer.nid;
                sum_entry->version = 0;
                sum_entry->ofs_in_node = 0;
                addr++;
-
-               /*
-                * In order to read next node page,
-                * we must clear PageUptodate flag.
-                */
-               ClearPageUptodate(page);
        }
-out:
        unlock_page(page);
+out:
        __free_pages(page, 0);
        return 0;
 }

diff --git a/fs/f2fs/recovery.c b/fs/f2fs/recovery.c
index 6b82e20..2d86eb2 100644 (file)
--- a/fs/f2fs/recovery.c
+++ b/fs/f2fs/recovery.c
@@ -112,11 +112,16 @@ static int find_fsync_dnodes(struct f2fs_sb_info *sbi, struct list_head *head)
        while (1) {
                struct fsync_inode_entry *entry;
 
-               if (f2fs_readpage(sbi, page, blkaddr, READ_SYNC))
+               err = f2fs_readpage(sbi, page, blkaddr, READ_SYNC);
+               if (err)
                        goto out;
 
-               if (cp_ver != cpver_of_node(page))
-                       goto out;
+               lock_page(page);
+
+               if (cp_ver != cpver_of_node(page)) {
+                       err = -EINVAL;
+                       goto unlock_out;
+               }
 
                if (!is_fsync_dnode(page))
                        goto next;
@@ -131,7 +136,7 @@ static int find_fsync_dnodes(struct f2fs_sb_info *sbi, struct list_head *head)
                        if (IS_INODE(page) && is_dent_dnode(page)) {
                                if (recover_inode_page(sbi, page)) {
                                        err = -ENOMEM;
-                                       goto out;
+                                       goto unlock_out;
                                }
                        }
 
@@ -139,14 +144,14 @@ static int find_fsync_dnodes(struct f2fs_sb_info *sbi, struct list_head *head)
                        entry = kmem_cache_alloc(fsync_entry_slab, GFP_NOFS);
                        if (!entry) {
                                err = -ENOMEM;
-                               goto out;
+                               goto unlock_out;
                        }
 
                        entry->inode = f2fs_iget(sbi->sb, ino_of_node(page));
                        if (IS_ERR(entry->inode)) {
                                err = PTR_ERR(entry->inode);
                                kmem_cache_free(fsync_entry_slab, entry);
-                               goto out;
+                               goto unlock_out;
                        }
 
                        list_add_tail(&entry->list, head);
@@ -155,15 +160,15 @@ static int find_fsync_dnodes(struct f2fs_sb_info *sbi, struct list_head *head)
                if (IS_INODE(page)) {
                        err = recover_inode(entry->inode, page);
                        if (err)
-                               goto out;
+                               goto unlock_out;
                }
 next:
                /* check next segment */
                blkaddr = next_blkaddr_of_node(page);
-               ClearPageUptodate(page);
        }
-out:
+unlock_out:
        unlock_page(page);
+out:
        __free_pages(page, 0);
        return err;
 }
@@ -319,8 +324,10 @@ static void recover_data(struct f2fs_sb_info *sbi,
                if (f2fs_readpage(sbi, page, blkaddr, READ_SYNC))
                        goto out;
 
+               lock_page(page);
+
                if (cp_ver != cpver_of_node(page))
-                       goto out;
+                       goto unlock_out;
 
                entry = get_fsync_inode(head, ino_of_node(page));
                if (!entry)
@@ -336,10 +343,10 @@ static void recover_data(struct f2fs_sb_info *sbi,
 next:
                /* check next segment */
                blkaddr = next_blkaddr_of_node(page);
-               ClearPageUptodate(page);
        }
-out:
+unlock_out:
        unlock_page(page);
+out:
        __free_pages(page, 0);
 
        allocate_new_segments(sbi);