Commit 7d8b1148 authored Jul 12, 2023 by Namjae Jeon

exfat: use kvmalloc_array/kvfree instead of kmalloc_array/kfree



The call stack shown below is a scenario in the Linux 4.19 kernel.
Allocating memory failed where exfat fs use kmalloc_array due to
system memory fragmentation, while the u-disk was inserted without
recognition.
Devices such as u-disk using the exfat file system are pluggable and
may be insert into the system at any time.
However, long-term running systems cannot guarantee the continuity of
physical memory. Therefore, it's necessary to address this issue.

Binder:2632_6: page allocation failure: order:4,
 mode:0x6040c0(GFP_KERNEL|__GFP_COMP), nodemask=(null)
Call trace:
[242178.097582]  dump_backtrace+0x0/0x4
[242178.097589]  dump_stack+0xf4/0x134
[242178.097598]  warn_alloc+0xd8/0x144
[242178.097603]  __alloc_pages_nodemask+0x1364/0x1384
[242178.097608]  kmalloc_order+0x2c/0x510
[242178.097612]  kmalloc_order_trace+0x40/0x16c
[242178.097618]  __kmalloc+0x360/0x408
[242178.097624]  load_alloc_bitmap+0x160/0x284
[242178.097628]  exfat_fill_super+0xa3c/0xe7c
[242178.097635]  mount_bdev+0x2e8/0x3a0
[242178.097638]  exfat_fs_mount+0x40/0x50
[242178.097643]  mount_fs+0x138/0x2e8
[242178.097649]  vfs_kern_mount+0x90/0x270
[242178.097655]  do_mount+0x798/0x173c
[242178.097659]  ksys_mount+0x114/0x1ac
[242178.097665]  __arm64_sys_mount+0x24/0x34
[242178.097671]  el0_svc_common+0xb8/0x1b8
[242178.097676]  el0_svc_handler+0x74/0x90
[242178.097681]  el0_svc+0x8/0x340

By analyzing the exfat code,we found that continuous physical memory
is not required here,so kvmalloc_array is used can solve this problem.

Signed-off-by: gaoming <gaoming20@hihonor.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>

parent 331d3f5c

balloc.c

+7 −3

Original line number	Diff line number	Diff line
		@@ -75,8 +75,12 @@ static int exfat_allocate_bitmap(struct super_block *sb,
		}
		sbi->map_sectors = ((need_map_size - 1) >>
		(sb->s_blocksize_bits)) + 1;
		sbi->vol_amap = kmalloc_array(sbi->map_sectors,
		#if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 12, 0)
		sbi->vol_amap = kvmalloc_array(sbi->map_sectors,
		sizeof(struct buffer_head *), GFP_KERNEL);
		#else
		sbi->vol_amap = vmalloc(sbi->map_sectors * sizeof(struct buffer_head *));
		#endif
		if (!sbi->vol_amap)
		return -ENOMEM;

		@@ -90,7 +94,7 @@ static int exfat_allocate_bitmap(struct super_block *sb,
		while (j < i)
		brelse(sbi->vol_amap[j++]);

		kfree(sbi->vol_amap);
		kvfree(sbi->vol_amap);
		sbi->vol_amap = NULL;
		return -EIO;
		}
		@@ -144,7 +148,7 @@ void exfat_free_bitmap(struct exfat_sb_info *sbi)
		for (i = 0; i < sbi->map_sectors; i++)
		__brelse(sbi->vol_amap[i]);

		kfree(sbi->vol_amap);
		kvfree(sbi->vol_amap);
		}

		int exfat_set_bitmap(struct inode *inode, unsigned int clu, bool sync)