ext4: Fix small file fragmentation
For small file block allocations, mballoc uses per cpu prealloc
space. Use goal block when searching for the right prealloc
space. Also make sure ext4_da_writepages tries to write
all the pages for small files in single attempt
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index d1906d9..7e91913e 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -2282,13 +2282,12 @@
static int ext4_da_writepages(struct address_space *mapping,
struct writeback_control *wbc)
{
- struct inode *inode = mapping->host;
handle_t *handle = NULL;
- int needed_blocks;
- int ret = 0;
- long to_write;
loff_t range_start = 0;
- long pages_skipped = 0;
+ struct inode *inode = mapping->host;
+ int needed_blocks, ret = 0, nr_to_writebump = 0;
+ long to_write, pages_skipped = 0;
+ struct ext4_sb_info *sbi = EXT4_SB(mapping->host->i_sb);
/*
* No pages to write? This is mainly a kludge to avoid starting
@@ -2297,6 +2296,16 @@
*/
if (!mapping->nrpages || !mapping_tagged(mapping, PAGECACHE_TAG_DIRTY))
return 0;
+ /*
+ * Make sure nr_to_write is >= sbi->s_mb_stream_request
+ * This make sure small files blocks are allocated in
+ * single attempt. This ensure that small files
+ * get less fragmented.
+ */
+ if (wbc->nr_to_write < sbi->s_mb_stream_request) {
+ nr_to_writebump = sbi->s_mb_stream_request - wbc->nr_to_write;
+ wbc->nr_to_write = sbi->s_mb_stream_request;
+ }
if (!wbc->range_cyclic)
/*
@@ -2377,7 +2386,7 @@
}
out_writepages:
- wbc->nr_to_write = to_write;
+ wbc->nr_to_write = to_write - nr_to_writebump;
wbc->range_start = range_start;
return ret;
}