On 2017年11月21日 15:41, Nikolay Borisov wrote:
>
>
> On 21.11.2017 09:21, Qu Wenruo wrote:
>> [BUG]
>> fstrim on some btrfs only trims the unallocated space, not trimming any
>> space in existing block groups.
>>
>> [CAUSE]
>> fstrim_range passed in by default fstrim will be:
>>
>> range->start = 0
>> range->len = fs_size (which equals with super->total_bytes)
>> range->min_len = 512
>>
>> However btrfs_trim_fs() following above parameter to search block groups
>> to trim.
>>
>> While it's quite possible that all chunks start beyond
>> super->total_bytes if the fs is balanced several times.
>>
>> In that case, btrfs will skip trimming block groups and only trim the
>> unallocated space of each device.
>>
>> [FIX]
>> For common full fs trimming range passed in, extent its len to (u64)-1
>> so we will iterate all block groups.
>>
>> And for custom fs trimming range, due to the fact that the range will
>> always be truncated by range [0, super->total_bytes), making custom fs
>> trimming range useless.
>>
>> Just return -ENOTTY for custom fs trimming range.
>>
>> Reported-by: Chris Murphy <lists@xxxxxxxxxxxxxxxxx>
>> Signed-off-by: Qu Wenruo <wqu@xxxxxxxx>
>
> I think we want this tagged for stable ?
Sounds pretty good.
Although I'm a little concerned about the ENOTTY return branch, not sure
if it will break script of some guys.
Thanks,
Qu
>
>
>> ---
>> fs/btrfs/extent-tree.c | 29 ++++++++++++++++++++++++-----
>> 1 file changed, 24 insertions(+), 5 deletions(-)
>>
>> diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
>> index 3a252d7af158..22bbcc8c4f6c 100644
>> --- a/fs/btrfs/extent-tree.c
>> +++ b/fs/btrfs/extent-tree.c
>> @@ -11024,12 +11024,31 @@ int btrfs_trim_fs(struct btrfs_fs_info *fs_info, struct fstrim_range *range)
>> int ret = 0;
>>
>> /*
>> - * try to trim all FS space, our block group may start from non-zero.
>> + * NOTE: Btrfs uses its own logical address space, where its first
>> + * chunk can start anywhere if it wants.
>> + * If we follow common start = 0 and len = fs_size from @range, we
>> + * can end up without trimming any block groups, since it's highly
>> + * possible all chunks start beyond that range.
>> + *
>> + * So if we want to trim the whole fs, extent the len to (u64)-1 to trim
>> + * all block groups.
>> + *
>> + * Also, since @range will always be truncated to fs size, manually
>> + * passing range to trim specified range doesn't make much sense.
>> + * (No mean to trim any block group whose bytenr starts beyond
>> + * @total_bytes)
>> + * So in that case, return -ENOTTY directly to prevent any custom trim
>> + * request.
>> */
>> - if (range->len == total_bytes)
>> - cache = btrfs_lookup_first_block_group(fs_info, range->start);
>> - else
>> - cache = btrfs_lookup_block_group(fs_info, range->start);
>> + if (range->start == 0 && range->len == total_bytes) {
>> + range->len = (u64)-1;
>> + } else {
>> + btrfs_info(fs_info,
>> + "trimming custom range is not supported due to the limitation of fstrim_range");
>> + return -ENOTTY;
>> + }
>> +
>> + cache = btrfs_lookup_first_block_group(fs_info, range->start);
>>
>> for (; cache; cache = next_block_group(fs_info, cache)) {
>> if (cache->key.objectid >= (range->start + range->len)) {
>>
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