Hulk Robot reported a BUG_ON:
==================================================================
kernel BUG at fs/ext4/mballoc.c:3211!
[...]
RIP: 0010:ext4_mb_mark_diskspace_used.cold+0x85/0x136f
[...]
Call Trace:
ext4_mb_new_blocks+0x9df/0x5d30
ext4_ext_map_blocks+0x1803/0x4d80
ext4_map_blocks+0x3a4/0x1a10
ext4_writepages+0x126d/0x2c30
do_writepages+0x7f/0x1b0
__filemap_fdatawrite_range+0x285/0x3b0
file_write_and_wait_range+0xb1/0x140
ext4_sync_file+0x1aa/0xca0
vfs_fsync_range+0xfb/0x260
do_fsync+0x48/0xa0
[...]
==================================================================
Above issue may happen as follows:
-------------------------------------
do_fsync
vfs_fsync_range
ext4_sync_file
file_write_and_wait_range
__filemap_fdatawrite_range
do_writepages
ext4_writepages
mpage_map_and_submit_extent
mpage_map_one_extent
ext4_map_blocks
ext4_mb_new_blocks
ext4_mb_normalize_request
>>> start + size <= ac->ac_o_ex.fe_logical
ext4_mb_regular_allocator
ext4_mb_simple_scan_group
ext4_mb_use_best_found
ext4_mb_new_preallocation
ext4_mb_new_inode_pa
ext4_mb_use_inode_pa
>>> set ac->ac_b_ex.fe_len <= 0
ext4_mb_mark_diskspace_used
>>> BUG_ON(ac->ac_b_ex.fe_len <= 0);
we can easily reproduce this problem with the following commands:
`fallocate -l100M disk`
`mkfs.ext4 -b 1024 -g 256 disk`
`mount disk /mnt`
`fsstress -d /mnt -l 0 -n 1000 -p 1`
The size must be smaller than or equal to EXT4_BLOCKS_PER_GROUP.
Therefore, "start + size <= ac->ac_o_ex.fe_logical" may occur
when the size is truncated. So start should be the start position of
the group where ac_o_ex.fe_logical is located after alignment.
In addition, when the value of fe_logical or EXT4_BLOCKS_PER_GROUP
is very large, the value calculated by start_off is more accurate.
Fixes: cd648b8a8fd5 ("ext4: trim allocation requests to group size")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Baokun Li <libaokun1@huawei.com>
---
V1->V2:
Replace round_down() with rounddown().
Modified comments.
V2->V3:
Convert EXT4_BLOCKS_PER_GROUP type to ext4_lblk_t
to avoid compilation warnings.
fs/ext4/mballoc.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 9f12f29bc346..4d3740fdff90 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -4104,6 +4104,15 @@ ext4_mb_normalize_request(struct ext4_allocation_context *ac,
size = size >> bsbits;
start = start_off >> bsbits;
+ /*
+ * For tiny groups (smaller than 8MB) the chosen allocation
+ * alignment may be larger than group size. Make sure the
+ * alignment does not move allocation to a different group which
+ * makes mballoc fail assertions later.
+ */
+ start = max(start, rounddown(ac->ac_o_ex.fe_logical,
+ (ext4_lblk_t)EXT4_BLOCKS_PER_GROUP(ac->ac_sb)));
+
/* don't cover already allocated blocks in selected range */
if (ar->pleft && start <= ar->lleft) {
size -= ar->lleft + 1 - start;
--
2.31.1On 22/05/28 07:00PM, Baokun Li wrote:
> Hulk Robot reported a BUG_ON:
> ==================================================================
> kernel BUG at fs/ext4/mballoc.c:3211!
> [...]
> RIP: 0010:ext4_mb_mark_diskspace_used.cold+0x85/0x136f
> [...]
> Call Trace:
> ext4_mb_new_blocks+0x9df/0x5d30
> ext4_ext_map_blocks+0x1803/0x4d80
> ext4_map_blocks+0x3a4/0x1a10
> ext4_writepages+0x126d/0x2c30
> do_writepages+0x7f/0x1b0
> __filemap_fdatawrite_range+0x285/0x3b0
> file_write_and_wait_range+0xb1/0x140
> ext4_sync_file+0x1aa/0xca0
> vfs_fsync_range+0xfb/0x260
> do_fsync+0x48/0xa0
> [...]
> ==================================================================
>
> Above issue may happen as follows:
> -------------------------------------
> do_fsync
> vfs_fsync_range
> ext4_sync_file
> file_write_and_wait_range
> __filemap_fdatawrite_range
> do_writepages
> ext4_writepages
> mpage_map_and_submit_extent
> mpage_map_one_extent
> ext4_map_blocks
> ext4_mb_new_blocks
> ext4_mb_normalize_request
> >>> start + size <= ac->ac_o_ex.fe_logical
> ext4_mb_regular_allocator
> ext4_mb_simple_scan_group
> ext4_mb_use_best_found
> ext4_mb_new_preallocation
> ext4_mb_new_inode_pa
> ext4_mb_use_inode_pa
> >>> set ac->ac_b_ex.fe_len <= 0
> ext4_mb_mark_diskspace_used
> >>> BUG_ON(ac->ac_b_ex.fe_len <= 0);
>
> we can easily reproduce this problem with the following commands:
> `fallocate -l100M disk`
> `mkfs.ext4 -b 1024 -g 256 disk`
> `mount disk /mnt`
> `fsstress -d /mnt -l 0 -n 1000 -p 1`
>
> The size must be smaller than or equal to EXT4_BLOCKS_PER_GROUP.
> Therefore, "start + size <= ac->ac_o_ex.fe_logical" may occur
> when the size is truncated. So start should be the start position of
> the group where ac_o_ex.fe_logical is located after alignment.
> In addition, when the value of fe_logical or EXT4_BLOCKS_PER_GROUP
> is very large, the value calculated by start_off is more accurate.
>
> Fixes: cd648b8a8fd5 ("ext4: trim allocation requests to group size")
> Reported-by: Hulk Robot <hulkci@huawei.com>
> Signed-off-by: Baokun Li <libaokun1@huawei.com>
> ---
> V1->V2:
> Replace round_down() with rounddown().
> Modified comments.
> V2->V3:
> Convert EXT4_BLOCKS_PER_GROUP type to ext4_lblk_t
> to avoid compilation warnings.
Looks good to me. Feel free to add -
Reviewed-by: Ritesh Harjani <ritesh.list@gmail.com>
>
> fs/ext4/mballoc.c | 9 +++++++++
> 1 file changed, 9 insertions(+)
>
在 2022/5/28 23:10, Ritesh Harjani 写道:
> On 22/05/28 07:00PM, Baokun Li wrote:
>> Hulk Robot reported a BUG_ON:
>> ==================================================================
>> kernel BUG at fs/ext4/mballoc.c:3211!
>> [...]
>> RIP: 0010:ext4_mb_mark_diskspace_used.cold+0x85/0x136f
>> [...]
>> Call Trace:
>> ext4_mb_new_blocks+0x9df/0x5d30
>> ext4_ext_map_blocks+0x1803/0x4d80
>> ext4_map_blocks+0x3a4/0x1a10
>> ext4_writepages+0x126d/0x2c30
>> do_writepages+0x7f/0x1b0
>> __filemap_fdatawrite_range+0x285/0x3b0
>> file_write_and_wait_range+0xb1/0x140
>> ext4_sync_file+0x1aa/0xca0
>> vfs_fsync_range+0xfb/0x260
>> do_fsync+0x48/0xa0
>> [...]
>> ==================================================================
>>
>> Above issue may happen as follows:
>> -------------------------------------
>> do_fsync
>> vfs_fsync_range
>> ext4_sync_file
>> file_write_and_wait_range
>> __filemap_fdatawrite_range
>> do_writepages
>> ext4_writepages
>> mpage_map_and_submit_extent
>> mpage_map_one_extent
>> ext4_map_blocks
>> ext4_mb_new_blocks
>> ext4_mb_normalize_request
>> >>> start + size <= ac->ac_o_ex.fe_logical
>> ext4_mb_regular_allocator
>> ext4_mb_simple_scan_group
>> ext4_mb_use_best_found
>> ext4_mb_new_preallocation
>> ext4_mb_new_inode_pa
>> ext4_mb_use_inode_pa
>> >>> set ac->ac_b_ex.fe_len <= 0
>> ext4_mb_mark_diskspace_used
>> >>> BUG_ON(ac->ac_b_ex.fe_len <= 0);
>>
>> we can easily reproduce this problem with the following commands:
>> `fallocate -l100M disk`
>> `mkfs.ext4 -b 1024 -g 256 disk`
>> `mount disk /mnt`
>> `fsstress -d /mnt -l 0 -n 1000 -p 1`
>>
>> The size must be smaller than or equal to EXT4_BLOCKS_PER_GROUP.
>> Therefore, "start + size <= ac->ac_o_ex.fe_logical" may occur
>> when the size is truncated. So start should be the start position of
>> the group where ac_o_ex.fe_logical is located after alignment.
>> In addition, when the value of fe_logical or EXT4_BLOCKS_PER_GROUP
>> is very large, the value calculated by start_off is more accurate.
>>
>> Fixes: cd648b8a8fd5 ("ext4: trim allocation requests to group size")
>> Reported-by: Hulk Robot <hulkci@huawei.com>
>> Signed-off-by: Baokun Li <libaokun1@huawei.com>
>> ---
>> V1->V2:
>> Replace round_down() with rounddown().
>> Modified comments.
>> V2->V3:
>> Convert EXT4_BLOCKS_PER_GROUP type to ext4_lblk_t
>> to avoid compilation warnings.
> Looks good to me. Feel free to add -
>
> Reviewed-by: Ritesh Harjani <ritesh.list@gmail.com>
>
>> fs/ext4/mballoc.c | 9 +++++++++
>> 1 file changed, 9 insertions(+)
>>
> .
>
Thank you for your review!
--
With Best Regards,
Baokun Li
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