On 17.01.20 г. 16:02 ч., Josef Bacik wrote:
> In order to keep track of where we have file extents on disk, and thus
> where it is safe to adjust the i_size to, we need to have a tree in
> place to keep track of the contiguous areas we have file extents for.
> Add helpers to use this tree, as it's not required for NO_HOLES file
> systems. We will use this by setting DIRTY for areas we know we have
> file extent item's set, and clearing it when we remove file extent items
> for truncation.
>
> Signed-off-by: Josef Bacik <josef@xxxxxxxxxxxxxx>
> Reviewed-by: Filipe Manana <fdmanana@xxxxxxxx>
> ---
> fs/btrfs/btrfs_inode.h | 5 +++
> fs/btrfs/ctree.h | 5 +++
> fs/btrfs/extent-io-tree.h | 1 +
> fs/btrfs/extent_io.c | 11 +++++
> fs/btrfs/file-item.c | 91 +++++++++++++++++++++++++++++++++++++++
> fs/btrfs/inode.c | 6 +++
> 6 files changed, 119 insertions(+)
>
> diff --git a/fs/btrfs/btrfs_inode.h b/fs/btrfs/btrfs_inode.h
> index 4e12a477d32e..d9dcbac513ed 100644
> --- a/fs/btrfs/btrfs_inode.h
> +++ b/fs/btrfs/btrfs_inode.h
> @@ -60,6 +60,11 @@ struct btrfs_inode {
> */
> struct extent_io_tree io_failure_tree;
>
> + /* keeps track of where we have extent items mapped in order to make
> + * sure our i_size adjustments are accurate.
> + */
> + struct extent_io_tree file_extent_tree;
> +
> /* held while logging the inode in tree-log.c */
> struct mutex log_mutex;
>
> diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
> index 00cf1641f1b9..8a2c1665baad 100644
> --- a/fs/btrfs/ctree.h
> +++ b/fs/btrfs/ctree.h
> @@ -2851,6 +2851,11 @@ void btrfs_extent_item_to_extent_map(struct btrfs_inode *inode,
> struct btrfs_file_extent_item *fi,
> const bool new_inline,
> struct extent_map *em);
> +int btrfs_inode_clear_file_extent_range(struct btrfs_inode *inode, u64 start,
> + u64 len);
> +int btrfs_inode_set_file_extent_range(struct btrfs_inode *inode, u64 start,
> + u64 len);
> +void btrfs_inode_safe_disk_i_size_write(struct inode *inode, u64 new_isize);
>
> /* inode.c */
> struct extent_map *btrfs_get_extent_fiemap(struct btrfs_inode *inode,
> diff --git a/fs/btrfs/extent-io-tree.h b/fs/btrfs/extent-io-tree.h
> index a3febe746c79..c8bcd2e3184c 100644
> --- a/fs/btrfs/extent-io-tree.h
> +++ b/fs/btrfs/extent-io-tree.h
> @@ -44,6 +44,7 @@ enum {
> IO_TREE_TRANS_DIRTY_PAGES,
> IO_TREE_ROOT_DIRTY_LOG_PAGES,
> IO_TREE_SELFTEST,
> + IO_TREE_INODE_FILE_EXTENT,
> };
>
> struct extent_io_tree {
> diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
> index 0d40cd7427ba..f9b223d827b3 100644
> --- a/fs/btrfs/extent_io.c
> +++ b/fs/btrfs/extent_io.c
> @@ -265,6 +265,15 @@ void __cold extent_io_exit(void)
> bioset_exit(&btrfs_bioset);
> }
>
> +/*
> + * For the file_extent_tree, we want to hold the inode lock when we lookup and
> + * update the disk_i_size, but lockdep will complain because our io_tree we hold
> + * the tree lock and get the inode lock when setting delalloc. These two things
> + * are unrelated, so make a class for the file_extent_tree so we don't get the
> + * two locking patterns mixed up.
> + */
> +static struct lock_class_key file_extent_tree_class;
> +
> void extent_io_tree_init(struct btrfs_fs_info *fs_info,
> struct extent_io_tree *tree, unsigned int owner,
> void *private_data)
> @@ -276,6 +285,8 @@ void extent_io_tree_init(struct btrfs_fs_info *fs_info,
> spin_lock_init(&tree->lock);
> tree->private_data = private_data;
> tree->owner = owner;
> + if (owner == IO_TREE_INODE_FILE_EXTENT)
> + lockdep_set_class(&tree->lock, &file_extent_tree_class);
> }
>
> void extent_io_tree_release(struct extent_io_tree *tree)
> diff --git a/fs/btrfs/file-item.c b/fs/btrfs/file-item.c
> index c2f365662d55..e5dc6c4b2f05 100644
> --- a/fs/btrfs/file-item.c
> +++ b/fs/btrfs/file-item.c
> @@ -23,6 +23,97 @@
> #define MAX_CSUM_ITEMS(r, size) (min_t(u32, __MAX_CSUM_ITEMS(r, size), \
> PAGE_SIZE))
>
> +/**
> + * @inode - the inode we want to update the disk_i_size for
> + * @new_isize - the isize we want to set to, 0 if we use i_size
> + *
> + * With NO_HOLES set this simply sets the disk_is_size to whatever i_size_read()
> + * returns as it is perfectly fine with a file that has holes without hole file
> + * extent items.
> + *
> + * However for !NO_HOLES we need to only return the area that is contiguous from
> + * the 0 offset of the file. Otherwise we could end up adjust i_size up to an
> + * extent that has a gap in between.
> + *
> + * Finally new_isize should only be set in the case of truncate where we're not
> + * ready to use i_size_read() as the limiter yet.
> + */
> +void btrfs_inode_safe_disk_i_size_write(struct inode *inode, u64 new_isize)
> +{
> + struct btrfs_fs_info *fs_info = BTRFS_I(inode)->root->fs_info;
> + u64 start, end, isize;
> + int ret;
> +
> + isize = new_isize ? new_isize : i_size_read(inode);
> + if (btrfs_fs_incompat(fs_info, NO_HOLES)) {
> + BTRFS_I(inode)->disk_i_size = isize;
> + return;
> + }
> +
> + spin_lock(&BTRFS_I(inode)->lock);
> + ret = find_first_extent_bit(&BTRFS_I(inode)->file_extent_tree, 0,
> + &start, &end, EXTENT_DIRTY, NULL);
> + if (!ret && start == 0)
> + isize = min(isize, end + 1);
> + else
> + isize = 0;
> + BTRFS_I(inode)->disk_i_size = isize;
> + spin_unlock(&BTRFS_I(inode)->lock);
> +}
> +
What if we have the following layout for an inode:
[----1M-EXTЕNT---][----2M-HOLE--------][------3M-EXTENT-----------]
In this case the idisk size should be 4m whereas with the above code it
will be 1M. Isn't this wrong?
