On Tue, Nov 21, 2017 at 7:21 AM, Qu Wenruo <w...@suse.com> 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 <li...@colorremedies.com> > Signed-off-by: Qu Wenruo <w...@suse.com> > --- > 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;
After the fs_trim program gets the value for the range's length and before it invokes the trim ioctl, the value might have changed, resulting in returning the enotty error below. > + } else { > + btrfs_info(fs_info, > + "trimming custom range is not supported due to the limitation > of fstrim_range"); I can't understand this message, and I doubt the average user/admin can. To me it seems this can be a lot more simple by ignoring the range, that is, always considering [0, (u64)-1[. After all, due to the way btrfs organizes space, the range does not make any sense and I doubt users/programs will have all the necessary knowledge and willing to compute a range that makes sense to btrfs based on the current block group layout of the fs... > + 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)) { > -- > 2.15.0 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in > the body of a message to majord...@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- Filipe David Manana, “Whether you think you can, or you think you can't — you're right.” -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html