Hello!
The following patch fixes the trimming on my /home Dual SSD BTRFS RAID 1
for quite some kernel releases already. Without it, it doesn´t trim
anything, with it, it trims possibly.
What would be required to get this or a similar fix into the kernel?
In either case this gets my:
Reported-and-tested-by: Martin Steigerwald <martin@xxxxxxxxxxxx>
I used trimming with this patch countless of times and scrub still tells
all is fine.
Thanks,
Martin
Am Samstag, 3. Januar 2015, 16:30:51 schrieb Lutz Euler:
> Commit 2cac13e41bf5b99ffc426bd28dfd2248df1dfa67, "fix trim 0 bytes after
> a device delete", said:
> A user reported a bug of btrfs's trim, that is we will trim 0 bytes
> after a device delete.
> The commit didn't attack the root of the problem so did not fix the bug
> except for a special case.
>
> For block discard, btrfs_trim_fs directly compares the range passed in
> against the filesystem's objectids. The former is bounded by the sum of
> the sizes of the devices of the filesystem, the latter is a completely
> unrelated set of intervals of 64-bit integers. The bug reported occurred
> as the smallest objectid was larger than the sum of the device sizes.
> The above mentioned commit only fixed the case where the smallest
> objectid is nonzero and the largest objectid less than the sum of the
> device sizes, but it still trims too little if the largest objectid is
> larger than that, and nothing in the reported situation.
>
> The current mapping between the given range and the objectids is thus
> clearly broken, so, to fix the bug and as a first step towards a
> complete solution, simply ignore the range parameter's start and length
> fields and always trim the whole filesystem. (While this makes it
> impossible to trim a filesystem only partly, due to the broken mapping
> this often didn't work anyway.)
>
> V2:
> - Rebased onto 3.9. (still applies to and works with 3.19-rc2)
> - Take range->minlen into account.
>
> Reported-by: Lutz Euler <lutz.euler@xxxxxxxxxx>
> Signed-off-by: Lutz Euler <lutz.euler@xxxxxxxxxx>
> ---
> fs/btrfs/extent-tree.c | 25 +++++++++++--------------
> 1 files changed, 11 insertions(+), 14 deletions(-)
>
> diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
> index cfb3cf7..81006c1 100644
> --- a/fs/btrfs/extent-tree.c
> +++ b/fs/btrfs/extent-tree.c
> @@ -8824,26 +8824,23 @@ int btrfs_trim_fs(struct btrfs_root *root, struct fstrim_range *range)
> u64 start;
> u64 end;
> u64 trimmed = 0;
> - u64 total_bytes = btrfs_super_total_bytes(fs_info->super_copy);
> int ret = 0;
>
> /*
> - * try to trim all FS space, our block group may start from non-zero.
> + * The range passed in is a subinterval of the interval from 0
> + * to the sum of the sizes of the devices of the filesystem.
> + * The objectid's used in the filesystem can span any set of
> + * subintervals of the interval from 0 to (u64)-1. As there is
> + * neither a simple nor an agreed upon mapping between these
> + * two ranges we ignore the range parameter's start and len
> + * fields and always trim the whole filesystem (that is, only
> + * the free space in allocated chunks).
> */
> - 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);
> + cache = btrfs_lookup_first_block_group(fs_info, 0);
>
> while (cache) {
> - if (cache->key.objectid >= (range->start + range->len)) {
> - btrfs_put_block_group(cache);
> - break;
> - }
> -
> - start = max(range->start, cache->key.objectid);
> - end = min(range->start + range->len,
> - cache->key.objectid + cache->key.offset);
> + start = cache->key.objectid;
> + end = cache->key.objectid + cache->key.offset;
>
> if (end - start >= range->minlen) {
> if (!block_group_cache_done(cache)) {
>
--
Martin 'Helios' Steigerwald - http://www.Lichtvoll.de
GPG: 03B0 0D6C 0040 0710 4AFA B82F 991B EAAC A599 84C7
--
To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
