If a file system has a large number of inodes per block group, all of
the metadata blocks in a flex_bg may be larger than what can fit in a
single block group. Unfortunately, ext4_alloc_group_tables() in
resize.c was never tested to see if it would handle this case
correctly, and there were a large number of bugs which caused the
following sequence to result in a BUG_ON:
kernel bug at fs/ext4/resize.c:409!
...
call trace:
[<ffffffff81256768>] ext4_flex_group_add+0x1448/0x1830
[<ffffffff81257de2>] ext4_resize_fs+0x7b2/0xe80
[<ffffffff8123ac50>] ext4_ioctl+0xbf0/0xf00
[<ffffffff811c111d>] do_vfs_ioctl+0x2dd/0x4b0
[<ffffffff811b9df2>] ? final_putname+0x22/0x50
[<ffffffff811c1371>] sys_ioctl+0x81/0xa0
[<ffffffff81676aa9>] system_call_fastpath+0x16/0x1b
code: c8 4c 89 df e8 41 96 f8 ff 44 89 e8 49 01 c4 44 29 6d d4 0
rip [<ffffffff81254fa1>] set_flexbg_block_bitmap+0x171/0x180
This can be reproduced with the following command sequence:
mke2fs -t ext4 -i 4096 /dev/vdd 1G
mount -t ext4 /dev/vdd /vdd
resize2fs /dev/vdd 8G
To fix this, we need to make sure the right thing happens when a block
group's inode table straddles two block groups, which means the
following bugs had to be fixed:
1) Not clearing the BLOCK_UNINIT flag in the second block group in
ext4_alloc_group_tables --- the was proximate cause of the BUG_ON.
2) Incorrectly determining how many block groups contained contiguous
free blocks in ext4_alloc_group_tables().
3) Incorrectly setting the start of the next block range to be marked
in use after a discontinuity in setup_new_flex_group_blocks().
Signed-off-by: "Theodore Ts'o" <tytso@xxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
---
fs/ext4/resize.c | 32 ++++++++++++++++++++------------
1 file changed, 20 insertions(+), 12 deletions(-)
diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
index c5adbb3..69a6261 100644
--- a/fs/ext4/resize.c
+++ b/fs/ext4/resize.c
@@ -243,6 +243,7 @@ static int ext4_alloc_group_tables(struct super_block *sb,
ext4_group_t group;
ext4_group_t last_group;
unsigned overhead;
+ __u16 uninit_mask = (flexbg_size > 1) ? ~EXT4_BG_BLOCK_UNINIT : ~0;
BUG_ON(flex_gd->count == 0 || group_data == NULL);
@@ -266,7 +267,7 @@ next_group:
src_group++;
for (; src_group <= last_group; src_group++) {
overhead = ext4_group_overhead_blocks(sb, src_group);
- if (overhead != 0)
+ if (overhead == 0)
last_blk += group_data[src_group - group].blocks_count;
else
break;
@@ -280,8 +281,7 @@ next_group:
group = ext4_get_group_number(sb, start_blk - 1);
group -= group_data[0].group;
group_data[group].free_blocks_count--;
- if (flexbg_size > 1)
- flex_gd->bg_flags[group] &= ~EXT4_BG_BLOCK_UNINIT;
+ flex_gd->bg_flags[group] &= uninit_mask;
}
/* Allocate inode bitmaps */
@@ -292,22 +292,30 @@ next_group:
group = ext4_get_group_number(sb, start_blk - 1);
group -= group_data[0].group;
group_data[group].free_blocks_count--;
- if (flexbg_size > 1)
- flex_gd->bg_flags[group] &= ~EXT4_BG_BLOCK_UNINIT;
+ flex_gd->bg_flags[group] &= uninit_mask;
}
/* Allocate inode tables */
for (; it_index < flex_gd->count; it_index++) {
- if (start_blk + EXT4_SB(sb)->s_itb_per_group > last_blk)
+ unsigned int itb = EXT4_SB(sb)->s_itb_per_group;
+ ext4_fsblk_t next_group_start;
+
+ if (start_blk + itb > last_blk)
goto next_group;
group_data[it_index].inode_table = start_blk;
- group = ext4_get_group_number(sb, start_blk - 1);
+ group = ext4_get_group_number(sb, start_blk);
+ next_group_start = ext4_group_first_block_no(sb, group + 1);
group -= group_data[0].group;
- group_data[group].free_blocks_count -=
- EXT4_SB(sb)->s_itb_per_group;
- if (flexbg_size > 1)
- flex_gd->bg_flags[group] &= ~EXT4_BG_BLOCK_UNINIT;
+ if (start_blk + itb > next_group_start) {
+ flex_gd->bg_flags[group + 1] &= uninit_mask;
+ overhead = start_blk + itb - next_group_start;
+ group_data[group + 1].free_blocks_count -= overhead;
+ itb -= overhead;
+ }
+
+ group_data[group].free_blocks_count -= itb;
+ flex_gd->bg_flags[group] &= uninit_mask;
start_blk += EXT4_SB(sb)->s_itb_per_group;
}
@@ -620,7 +628,7 @@ handle_ib:
if (err)
goto out;
count = group_table_count[j];
- start = group_data[i].block_bitmap;
+ start = (&group_data[i].block_bitmap)[j];
block = start;
}
--
1.8.5.rc3.362.gdf10213
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