ext4: Don't normalize an falloc request if it can fit in 1 extent.

If an fallocate request fits in EXT_UNINIT_MAX_LEN, then set the
EXT4_GET_BLOCKS_NO_NORMALIZE flag. For larger fallocate requests,
let mballoc.c normalize the request.

This fixes a problem where large requests were being split into
non-contiguous extents due to commit 556b27abf73: ext4: do not
normalize block requests from fallocate.

Testing:
*) Checked that 8.x MB falloc'ed files are still laid down next to
each other (contiguously).
*) Checked that the maximum size extent (127.9MB) is allocated as 1
extent.
*) Checked that a 1GB file is somewhat contiguous (often 5-6
non-contiguous extents now).
*) Checked that a 120MB file can still be falloc'ed even if there are
no single extents large enough to hold it.

Signed-off-by: Greg Harm <gharm@google.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index a5c8caa..2798945 100644 (file)
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -4337,10 +4337,16 @@ long ext4_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
                trace_ext4_fallocate_exit(inode, offset, max_blocks, ret);
                return ret;
        }
-       flags = EXT4_GET_BLOCKS_CREATE_UNINIT_EXT |
-               EXT4_GET_BLOCKS_NO_NORMALIZE;
+       flags = EXT4_GET_BLOCKS_CREATE_UNINIT_EXT;
        if (mode & FALLOC_FL_KEEP_SIZE)
                flags |= EXT4_GET_BLOCKS_KEEP_SIZE;
+       /*
+        * Don't normalize the request if it can fit in one extent so
+        * that it doesn't get unnecessarily split into multiple
+        * extents.
+        */
+       if (len <= EXT_UNINIT_MAX_LEN << blkbits)
+               flags |= EXT4_GET_BLOCKS_NO_NORMALIZE;
 retry:
        while (ret >= 0 && ret < max_blocks) {
                map.m_lblk = map.m_lblk + ret;