On 17/10/13 08:45, Junxiao Bi wrote:
> On 10/13/2017 03:12 AM, Ashish Samant wrote:
>> The first cluster group descriptor is not stored at the start of the group
>> but at an offset from the start. We need to take this into account while
>> doing fstrim on the first cluster group. Otherwise we will wrongly start
>> fstrim a few blocks after the desired start block and the range can cross
>> over into the next cluster group and zero out the group descriptor there.
>> This can cause filesytem corruption that cannot be fixed by fsck.
>>
>> Signed-off-by: Ashish Samant <ashish.sam...@oracle.com>
>> Cc: sta...@vger.kernel.org
> Looks good.
>
> Reviewed-by: Junxiao Bi <junxiao...@oracle.com>
>
Reviewed-by: Joseph Qi <jiangqi...@gmail.com>
>> ---
>> fs/ocfs2/alloc.c | 24 ++++++++++++++++++------
>> 1 file changed, 18 insertions(+), 6 deletions(-)
>>
>> diff --git a/fs/ocfs2/alloc.c b/fs/ocfs2/alloc.c
>> index a177eae..addd7c5 100644
>> --- a/fs/ocfs2/alloc.c
>> +++ b/fs/ocfs2/alloc.c
>> @@ -7304,13 +7304,24 @@ int ocfs2_truncate_inline(struct inode *inode,
>> struct buffer_head *di_bh,
>>
>> static int ocfs2_trim_extent(struct super_block *sb,
>> struct ocfs2_group_desc *gd,
>> - u32 start, u32 count)
>> + u64 group, u32 start, u32 count)
>> {
>> u64 discard, bcount;
>> + struct ocfs2_super *osb = OCFS2_SB(sb);
>>
>> bcount = ocfs2_clusters_to_blocks(sb, count);
>> - discard = le64_to_cpu(gd->bg_blkno) +
>> - ocfs2_clusters_to_blocks(sb, start);
>> + discard = ocfs2_clusters_to_blocks(sb, start);
>> +
>> + /*
>> + * For the first cluster group, the gd->bg_blkno is not at the start
>> + * of the group, but at an offset from the start. If we add it while
>> + * calculating discard for first group, we will wrongly start fstrim a
>> + * few blocks after the desried start block and the range can cross
>> + * over into the next cluster group. So, add it only if this is not
>> + * the first cluster group.
>> + */
>> + if (group != osb->first_cluster_group_blkno)
>> + discard += le64_to_cpu(gd->bg_blkno);
>>
>> trace_ocfs2_trim_extent(sb, (unsigned long long)discard, bcount);
>>
>> @@ -7318,7 +7329,7 @@ static int ocfs2_trim_extent(struct super_block *sb,
>> }
>>
>> static int ocfs2_trim_group(struct super_block *sb,
>> - struct ocfs2_group_desc *gd,
>> + struct ocfs2_group_desc *gd, u64 group,
>> u32 start, u32 max, u32 minbits)
>> {
>> int ret = 0, count = 0, next;
>> @@ -7337,7 +7348,7 @@ static int ocfs2_trim_group(struct super_block *sb,
>> next = ocfs2_find_next_bit(bitmap, max, start);
>>
>> if ((next - start) >= minbits) {
>> - ret = ocfs2_trim_extent(sb, gd,
>> + ret = ocfs2_trim_extent(sb, gd, group,
>> start, next - start);
>> if (ret < 0) {
>> mlog_errno(ret);
>> @@ -7435,7 +7446,8 @@ int ocfs2_trim_fs(struct super_block *sb, struct
>> fstrim_range *range)
>> }
>>
>> gd = (struct ocfs2_group_desc *)gd_bh->b_data;
>> - cnt = ocfs2_trim_group(sb, gd, first_bit, last_bit, minlen);
>> + cnt = ocfs2_trim_group(sb, gd, group,
>> + first_bit, last_bit, minlen);
>> brelse(gd_bh);
>> gd_bh = NULL;
>> if (cnt < 0) {
>>
>
>
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