On Thu, May 14, 2020 at 8:35 AM Qu Wenruo <wqu@xxxxxxxx> wrote:
>
> There are a lot of root owner check in btrfs_truncate_inode_items()
> like:
>
> if (test_bit(BTRFS_ROOT_SHAREABLE, &root->state) ||
> root == fs_info->tree_root)
>
> But considering that, there are only those trees can have INODE_ITEMs:
> - tree root (For v1 space cache)
> - subvolume trees
> - tree reloc trees
> - data reloc tree
> - log trees
>
> And since subvolume/tree reloc/data reloc trees all have SHAREABLE bit,
> and we're checking tree root manually, so above check is just excluding
> log trees.
>
> This patch will replace two of such checks to a much simpler one:
>
> if (root->root_key.objectid != BTRFS_TREE_LOG_OBJECTID)
>
> This would merge btrfs_drop_extent_cache() and lock_extent_bits() call
> into the same if branch.
>
> Also since we're here, add one comment explaining why we don't want to
> call lock_extent_bits()/drop_extent_cache() on log trees.
>
> Finally replace ALIGN()/ALIGN_DOWN() to round_up()/round_down(), as I'm
> always bad at determing the alignement direction.
>
> Signed-off-by: Qu Wenruo <wqu@xxxxxxxx>
> ---
> fs/btrfs/inode.c | 27 ++++++++++++++-------------
> 1 file changed, 14 insertions(+), 13 deletions(-)
>
> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> index a6c26c10ffc5..771af55038bf 100644
> --- a/fs/btrfs/inode.c
> +++ b/fs/btrfs/inode.c
> @@ -4101,7 +4101,7 @@ int btrfs_truncate_inode_items(struct btrfs_trans_handle *trans,
> u64 bytes_deleted = 0;
> bool be_nice = false;
> bool should_throttle = false;
> - const u64 lock_start = ALIGN_DOWN(new_size, fs_info->sectorsize);
> + const u64 lock_start = round_down(new_size, fs_info->sectorsize);
Hum, seriously? Why does ALIGN_DOWN confuses you? ALIGN, means to
align, and the DOWN part is very explicit about the direction.
> struct extent_state *cached_state = NULL;
>
> BUG_ON(new_size > 0 && min_type != BTRFS_EXTENT_DATA_KEY);
> @@ -4121,20 +4121,22 @@ int btrfs_truncate_inode_items(struct btrfs_trans_handle *trans,
> return -ENOMEM;
> path->reada = READA_BACK;
>
> - if (root->root_key.objectid != BTRFS_TREE_LOG_OBJECTID)
> - lock_extent_bits(&BTRFS_I(inode)->io_tree, lock_start, (u64)-1,
> - &cached_state);
> -
> /*
> - * We want to drop from the next block forward in case this new size is
> - * not block aligned since we will be keeping the last block of the
> - * extent just the way it is.
> + * There will be a lot of exceptions for log trees, as log inodes are
> + * not real inodes, but an anchor for logged inodes.
This is a very confusing sentence, you're saying logged inodes are an
"anchor" (whatever that means) to themselves.
Either leave nothing as it was, or just say log tree operations aren't
supposed to change anything on the inodes.
Thanks.
> */
> - if (test_bit(BTRFS_ROOT_SHAREABLE, &root->state) ||
> - root == fs_info->tree_root)
> - btrfs_drop_extent_cache(BTRFS_I(inode), ALIGN(new_size,
> + if (root->root_key.objectid != BTRFS_TREE_LOG_OBJECTID) {
> + /*
> + * We want to drop from the next block forward in case this
> + * new size is not block aligned since we will be keeping the
> + * last block of the extent just the way it is.
> + */
> + lock_extent_bits(&BTRFS_I(inode)->io_tree, lock_start, (u64)-1,
> + &cached_state);
> + btrfs_drop_extent_cache(BTRFS_I(inode), round_up(new_size,
> fs_info->sectorsize),
> (u64)-1, 0);
> + }
>
> /*
> * This function is also used to drop the items in the log tree before
> @@ -4335,8 +4337,7 @@ int btrfs_truncate_inode_items(struct btrfs_trans_handle *trans,
> should_throttle = false;
>
> if (found_extent &&
> - (test_bit(BTRFS_ROOT_SHAREABLE, &root->state) ||
> - root == fs_info->tree_root)) {
> + root->root_key.objectid != BTRFS_TREE_LOG_OBJECTID) {
> struct btrfs_ref ref = { 0 };
>
> bytes_deleted += extent_num_bytes;
> --
> 2.26.2
>
--
Filipe David Manana,
“Whether you think you can, or you think you can't — you're right.”
