From 665d3e0af4d35acf9a5f58dfd471bc27dbf55880 Mon Sep 17 00:00:00 2001 From: Baokun Li Date: Mon, 23 Oct 2023 09:30:57 +0800 Subject: [PATCH] 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: Baokun Li Reviewed-by: Jan Kara Link: https://lore.kernel.org/r/20231023013057.2117948-5-libaokun1@huawei.com Signed-off-by: Theodore Ts'o --- fs/ext4/resize.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c index e168a9f596001c..4d4a5a32e310d4 100644 --- a/fs/ext4/resize.c +++ b/fs/ext4/resize.c @@ -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;