[PATCH 04/49] ext4: Fallback to vmalloc if kmalloc can't allocate s_flex_groups array

Theodore Ts'o
2009-06-08T19:24:56Z

For very large filesystems, the s_flex_groups array can get quite big.
For example, a filesystem that can be resized up to 16TB will have
8192 flex groups (assuming the default flex_bg size of 16), so the
array is 96k, which is *very* marginal for kmalloc(). On the other
hand, a 160GB filesystem without the resize_inode feature will only
require 960 bytes. So we try to allocate the array first using
kmalloc(), and if that fails, we'll try to use vmalloc() instead.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
---
fs/ext4/super.c | 22 +++++++++++++++++++---
1 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 2958f4e..3f4475d 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -20,6 +20,7 @@
#include <linux/string.h>
#include <linux/fs.h>
#include <linux/time.h>
+#include <linux/vmalloc.h>
#include <linux/jbd2.h>
#include <linux/slab.h>
#include <linux/init.h>
@@ -586,7 +587,10 @@ static void ext4_put_super(struct super_block *sb)
for (i = 0; i < sbi->s_gdb_count; i++)
brelse(sbi->s_group_desc[i]);
kfree(sbi->s_group_desc);
- kfree(sbi->s_flex_groups);
+ if (is_vmalloc_addr(sbi->s_flex_groups))
+ vfree(sbi->s_flex_groups);
+ else
+ kfree(sbi->s_flex_groups);
percpu_counter_destroy(&sbi->s_freeblocks_counter);
percpu_counter_destroy(&sbi->s_freeinodes_counter);
percpu_counter_destroy(&sbi->s_dirs_counter);
@@ -1620,6 +1624,7 @@ static int ext4_fill_flex_info(struct super_block *sb)
ext4_group_t flex_group_count;
ext4_group_t flex_group;
int groups_per_flex = 0;
+ size_t size;
int i;

if (!sbi->s_es->s_log_groups_per_flex) {
@@ -1634,8 +1639,13 @@ static int ext4_fill_flex_info(struct super_block *sb)
flex_group_count = ((sbi->s_groups_count + groups_per_flex - 1) +
((le16_to_cpu(sbi->s_es->s_reserved_gdt_blocks) + 1) <<
EXT4_DESC_PER_BLOCK_BITS(sb))) / groups_per_flex;
- sbi->s_flex_groups = kzalloc(flex_group_count *
- sizeof(struct flex_groups), GFP_KERNEL);
+ size = flex_group_count * sizeof(struct flex_groups);
+ sbi->s_flex_groups = kzalloc(size, GFP_KERNEL);
+ if (sbi->s_flex_groups == NULL) {
+ sbi->s_flex_groups = vmalloc(size);
+ if (sbi->s_flex_groups)
+ memset(sbi->s_flex_groups, 0, size);
+ }
if (sbi->s_flex_groups == NULL) {
printk(KERN_ERR "EXT4-fs: not enough memory for "
"%u flex groups\n", flex_group_count);
@@ -2842,6 +2852,12 @@ failed_mount4:
sbi->s_journal = NULL;
}
failed_mount3:
+ if (sbi->s_flex_groups) {
+ if (is_vmalloc_addr(sbi->s_flex_groups))
+ vfree(sbi->s_flex_groups);
+ else
+ kfree(sbi->s_flex_groups);
+ }
percpu_counter_destroy(&sbi->s_freeblocks_counter);
percpu_counter_destroy(&sbi->s_freeinodes_counter);
percpu_counter_destroy(&sbi->s_dirs_counter);
--
1.6.3.2.1.gb9f7d.dirty