f2fs: disable the extent cache ops on high fragmented files
The f2fs manages an extent cache to search a number of consecutive data blocks
very quickly.
However it conducts unnecessary cache operations if the file is highly
fragmented with no valid extent cache.
In such the case, we don't need to handle the extent cache, but just can disable
the cache facility.
Nevertheless, this patch gives one more chance to enable the extent cache.
For example,
1. create a file
2. write data sequentially which produces a large valid extent cache
3. update some data, resulting in a fragmented extent
4. if the fragmented extent is too small, then drop extent cache
5. close the file
6. open the file again
7. give another chance to make a new extent cache
8. write data sequentially again which creates another big extent cache.
...
Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>
diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 5920639..2e54522 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -71,6 +71,9 @@
pgoff_t start_fofs, end_fofs;
block_t start_blkaddr;
+ if (is_inode_flag_set(fi, FI_NO_EXTENT))
+ return 0;
+
read_lock(&fi->ext.ext_lock);
if (fi->ext.len == 0) {
read_unlock(&fi->ext.ext_lock);
@@ -109,6 +112,7 @@
struct f2fs_inode_info *fi = F2FS_I(dn->inode);
pgoff_t fofs, start_fofs, end_fofs;
block_t start_blkaddr, end_blkaddr;
+ int need_update = true;
f2fs_bug_on(blk_addr == NEW_ADDR);
fofs = start_bidx_of_node(ofs_of_node(dn->node_page), fi) +
@@ -117,6 +121,9 @@
/* Update the page address in the parent node */
__set_data_blkaddr(dn, blk_addr);
+ if (is_inode_flag_set(fi, FI_NO_EXTENT))
+ return;
+
write_lock(&fi->ext.ext_lock);
start_fofs = fi->ext.fofs;
@@ -163,14 +170,21 @@
fofs - start_fofs + 1;
fi->ext.len -= fofs - start_fofs + 1;
}
- goto end_update;
+ } else {
+ need_update = false;
}
- write_unlock(&fi->ext.ext_lock);
- return;
+ /* Finally, if the extent is very fragmented, let's drop the cache. */
+ if (fi->ext.len < F2FS_MIN_EXTENT_LEN) {
+ fi->ext.len = 0;
+ set_inode_flag(fi, FI_NO_EXTENT);
+ need_update = true;
+ }
end_update:
write_unlock(&fi->ext.ext_lock);
- sync_inode_page(dn);
+ if (need_update)
+ sync_inode_page(dn);
+ return;
}
struct page *find_data_page(struct inode *inode, pgoff_t index, bool sync)