Commit 665d3e0a authored by Baokun Li's avatar Baokun Li Committed by Theodore Ts'o
Browse files

ext4: reduce unnecessary memory allocation in alloc_flex_gd() 



When a large flex_bg file system is resized, the number of groups to be
added may be small, and a large amount of memory that will not be used will
be allocated. Therefore, resize_bg can be set to the size after the number
of new_group_data to be used is aligned upwards to the power of 2. This
does not affect the disk layout after online resize and saves some memory.

Signed-off-by: default avatarBaokun Li <libaokun1@huawei.com>
Reviewed-by: default avatarJan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20231023013057.2117948-5-libaokun1@huawei.com


Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
parent 5d1935ac

fs/ext4/resize.c

+12 −2
Original line number Diff line number Diff line
@@ -235,8 +235,10 @@ struct ext4_new_flex_group_data { 
 *

 * Returns NULL on failure otherwise address of the allocated structure.

 */

static struct ext4_new_flex_group_data *alloc_flex_gd(unsigned int flexbg_size)

static struct ext4_new_flex_group_data *alloc_flex_gd(unsigned int flexbg_size,

				ext4_group_t o_group, ext4_group_t n_group)

{

	ext4_group_t last_group;

	struct ext4_new_flex_group_data *flex_gd;



	flex_gd = kmalloc(sizeof(*flex_gd), GFP_NOFS);
@@ -248,6 +250,14 @@ static struct ext4_new_flex_group_data *alloc_flex_gd(unsigned int flexbg_size) 
	else

		flex_gd->resize_bg = flexbg_size;



	/* Avoid allocating large 'groups' array if not needed */

	last_group = o_group | (flex_gd->resize_bg - 1);

	if (n_group <= last_group)

		flex_gd->resize_bg = 1 << fls(n_group - o_group + 1);

	else if (n_group - last_group < flex_gd->resize_bg)

		flex_gd->resize_bg = 1 << max(fls(last_group - o_group + 1),

					      fls(n_group - last_group));



	flex_gd->groups = kmalloc_array(flex_gd->resize_bg,

					sizeof(struct ext4_new_group_data),

					GFP_NOFS);
@@ -2131,7 +2141,7 @@ int ext4_resize_fs(struct super_block *sb, ext4_fsblk_t n_blocks_count) 
	if (err)

		goto out;



	flex_gd = alloc_flex_gd(flexbg_size);

	flex_gd = alloc_flex_gd(flexbg_size, o_group, n_group);

	if (flex_gd == NULL) {

		err = -ENOMEM;

		goto out;