| Message ID | 20180723062246.2885-1-wqu@suse.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | btrfs: extent-tree: Remove dead alignment check | expand |
On 2018年07月23日 14:22, Qu Wenruo wrote: > In find_free_extent() under checks: tag, we have the following code > > ------ > search_start = ALIGN(offset, fs_info->stripesize); > /* move on to the next group */ > if (search_start + num_bytes > > block_group->key.objectid + block_group->key.offset) { > btrfs_add_free_space(block_group, offset, num_bytes); > goto loop; > } > if (offset < search_start) > btrfs_add_free_space(block_group, offset, > search_start - offset); > BUG_ON(offset > search_start); > ------ > > However ALIGN() is rounding down, thus @search_start <= @offset. Well, ALIGN() is rounding up, so this is completely wrong. But still we have some conflicting BUG_ON() against ALIGN(). I'll update the patch and hopes no one found my stupid error. Thanks, Qu > > That later (offset < search_start) check will never be true, but that > BUG_ON(offset > search_start) can be triggered as long as our @offset is > not aligned to @stripesize. > > However we never has such report on this BUG_ON(), which means the > search result @offset is always aligned to @fs_info->stripesize (which > is also set to sector size at mkfs time), or it's handled by block group > range check. > > Anyway, remove such dead unalignment check. > > Signed-off-by: Qu Wenruo <wqu@suse.com> > --- > fs/btrfs/extent-tree.c | 7 +------ > 1 file changed, 1 insertion(+), 6 deletions(-) > > diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c > index f18e86177067..48a2aec7dc59 100644 > --- a/fs/btrfs/extent-tree.c > +++ b/fs/btrfs/extent-tree.c > @@ -7754,7 +7754,7 @@ static noinline int find_free_extent(struct btrfs_fs_info *fs_info, > goto loop; > } > checks: > - search_start = ALIGN(offset, fs_info->stripesize); > + search_start = round_down(offset, fs_info->stripesize); > > /* move on to the next group */ > if (search_start + num_bytes > > @@ -7763,11 +7763,6 @@ static noinline int find_free_extent(struct btrfs_fs_info *fs_info, > goto loop; > } > > - if (offset < search_start) > - btrfs_add_free_space(block_group, offset, > - search_start - offset); > - BUG_ON(offset > search_start); > - > ret = btrfs_add_reserved_bytes(block_group, ram_bytes, > num_bytes, delalloc); > if (ret == -EAGAIN) { >
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c index f18e86177067..48a2aec7dc59 100644 --- a/fs/btrfs/extent-tree.c +++ b/fs/btrfs/extent-tree.c @@ -7754,7 +7754,7 @@ static noinline int find_free_extent(struct btrfs_fs_info *fs_info, goto loop; } checks: - search_start = ALIGN(offset, fs_info->stripesize); + search_start = round_down(offset, fs_info->stripesize); /* move on to the next group */ if (search_start + num_bytes > @@ -7763,11 +7763,6 @@ static noinline int find_free_extent(struct btrfs_fs_info *fs_info, goto loop; } - if (offset < search_start) - btrfs_add_free_space(block_group, offset, - search_start - offset); - BUG_ON(offset > search_start); - ret = btrfs_add_reserved_bytes(block_group, ram_bytes, num_bytes, delalloc); if (ret == -EAGAIN) {
In find_free_extent() under checks: tag, we have the following code ------ search_start = ALIGN(offset, fs_info->stripesize); /* move on to the next group */ if (search_start + num_bytes > block_group->key.objectid + block_group->key.offset) { btrfs_add_free_space(block_group, offset, num_bytes); goto loop; } if (offset < search_start) btrfs_add_free_space(block_group, offset, search_start - offset); BUG_ON(offset > search_start); ------ However ALIGN() is rounding down, thus @search_start <= @offset. That later (offset < search_start) check will never be true, but that BUG_ON(offset > search_start) can be triggered as long as our @offset is not aligned to @stripesize. However we never has such report on this BUG_ON(), which means the search result @offset is always aligned to @fs_info->stripesize (which is also set to sector size at mkfs time), or it's handled by block group range check. Anyway, remove such dead unalignment check. Signed-off-by: Qu Wenruo <wqu@suse.com> --- fs/btrfs/extent-tree.c | 7 +------ 1 file changed, 1 insertion(+), 6 deletions(-)