Commit 3c6fe770 authored Oct 31, 2011 by Greg Harm Committed by Theodore Ts'o Oct 31, 2011

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 556b27ab: 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>

parent 4af83508

fs/ext4/extents.c

+8 −2

Original line number	Original line	Diff line number	Diff line
	@@ -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);		trace_ext4_fallocate_exit(inode, offset, max_blocks, ret);
	return ret;		return ret;
	}		}
	flags = EXT4_GET_BLOCKS_CREATE_UNINIT_EXT \|		flags = EXT4_GET_BLOCKS_CREATE_UNINIT_EXT;
	EXT4_GET_BLOCKS_NO_NORMALIZE;
	if (mode & FALLOC_FL_KEEP_SIZE)		if (mode & FALLOC_FL_KEEP_SIZE)
	flags \|= EXT4_GET_BLOCKS_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:		retry:
	while (ret >= 0 && ret < max_blocks) {		while (ret >= 0 && ret < max_blocks) {
	map.m_lblk = map.m_lblk + ret;		map.m_lblk = map.m_lblk + ret;