ext4: add ext4_split_extent_at() and ext4_split_extent()
Add two functions: ext4_split_extent_at(), which splits an extent into two extents at given logical block, and ext4_split_extent() which splits an extent into three extents. Signed-off-by: Yongqiang Yang <xiaoqiangnk@gmail.com> Signed-off-by: "Theodore Ts'o" <tytso@mit.edu> Tested-by: Allison Henderson <achender@linux.vnet.ibm.com>
This commit is contained in:
Yongqiang Yang
Theodore Ts'o
parent
197217a5af
commit
47ea3bb59c
@ -2554,6 +2554,193 @@ static int ext4_ext_zeroout(struct inode *inode, struct ext4_extent *ex)
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return ret;
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}
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/*
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* used by extent splitting.
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*/
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#define EXT4_EXT_MAY_ZEROOUT 0x1 /* safe to zeroout if split fails \
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due to ENOSPC */
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#define EXT4_EXT_MARK_UNINIT1 0x2 /* mark first half uninitialized */
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#define EXT4_EXT_MARK_UNINIT2 0x4 /* mark second half uninitialized */
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/*
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* ext4_split_extent_at() splits an extent at given block.
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*
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* @handle: the journal handle
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* @inode: the file inode
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* @path: the path to the extent
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* @split: the logical block where the extent is splitted.
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* @split_flags: indicates if the extent could be zeroout if split fails, and
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* the states(init or uninit) of new extents.
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* @flags: flags used to insert new extent to extent tree.
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*
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*
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* Splits extent [a, b] into two extents [a, @split) and [@split, b], states
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* of which are deterimined by split_flag.
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*
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* There are two cases:
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* a> the extent are splitted into two extent.
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* b> split is not needed, and just mark the extent.
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*
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* return 0 on success.
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*/
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static int ext4_split_extent_at(handle_t *handle,
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struct inode *inode,
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struct ext4_ext_path *path,
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ext4_lblk_t split,
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int split_flag,
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int flags)
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{
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ext4_fsblk_t newblock;
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ext4_lblk_t ee_block;
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struct ext4_extent *ex, newex, orig_ex;
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struct ext4_extent *ex2 = NULL;
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unsigned int ee_len, depth;
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int err = 0;
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ext_debug("ext4_split_extents_at: inode %lu, logical"
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"block %llu\n", inode->i_ino, (unsigned long long)split);
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ext4_ext_show_leaf(inode, path);
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depth = ext_depth(inode);
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ex = path[depth].p_ext;
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ee_block = le32_to_cpu(ex->ee_block);
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ee_len = ext4_ext_get_actual_len(ex);
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newblock = split - ee_block + ext4_ext_pblock(ex);
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BUG_ON(split < ee_block || split >= (ee_block + ee_len));
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err = ext4_ext_get_access(handle, inode, path + depth);
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if (err)
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goto out;
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if (split == ee_block) {
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/*
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* case b: block @split is the block that the extent begins with
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* then we just change the state of the extent, and splitting
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* is not needed.
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*/
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if (split_flag & EXT4_EXT_MARK_UNINIT2)
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ext4_ext_mark_uninitialized(ex);
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else
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ext4_ext_mark_initialized(ex);
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if (!(flags & EXT4_GET_BLOCKS_PRE_IO))
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ext4_ext_try_to_merge(inode, path, ex);
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err = ext4_ext_dirty(handle, inode, path + depth);
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goto out;
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}
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/* case a */
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memcpy(&orig_ex, ex, sizeof(orig_ex));
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ex->ee_len = cpu_to_le16(split - ee_block);
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if (split_flag & EXT4_EXT_MARK_UNINIT1)
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ext4_ext_mark_uninitialized(ex);
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/*
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* path may lead to new leaf, not to original leaf any more
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* after ext4_ext_insert_extent() returns,
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*/
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err = ext4_ext_dirty(handle, inode, path + depth);
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if (err)
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goto fix_extent_len;
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ex2 = &newex;
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ex2->ee_block = cpu_to_le32(split);
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ex2->ee_len = cpu_to_le16(ee_len - (split - ee_block));
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ext4_ext_store_pblock(ex2, newblock);
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if (split_flag & EXT4_EXT_MARK_UNINIT2)
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ext4_ext_mark_uninitialized(ex2);
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err = ext4_ext_insert_extent(handle, inode, path, &newex, flags);
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if (err == -ENOSPC && (EXT4_EXT_MAY_ZEROOUT & split_flag)) {
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err = ext4_ext_zeroout(inode, &orig_ex);
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if (err)
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goto fix_extent_len;
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/* update the extent length and mark as initialized */
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ex->ee_len = cpu_to_le32(ee_len);
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ext4_ext_try_to_merge(inode, path, ex);
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err = ext4_ext_dirty(handle, inode, path + depth);
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goto out;
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} else if (err)
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goto fix_extent_len;
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out:
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ext4_ext_show_leaf(inode, path);
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return err;
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fix_extent_len:
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ex->ee_len = orig_ex.ee_len;
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ext4_ext_dirty(handle, inode, path + depth);
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return err;
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}
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/*
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* ext4_split_extents() splits an extent and mark extent which is covered
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* by @map as split_flags indicates
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*
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* It may result in splitting the extent into multiple extents (upto three)
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* There are three possibilities:
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* a> There is no split required
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* b> Splits in two extents: Split is happening at either end of the extent
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* c> Splits in three extents: Somone is splitting in middle of the extent
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*
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*/
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static int ext4_split_extent(handle_t *handle,
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struct inode *inode,
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struct ext4_ext_path *path,
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struct ext4_map_blocks *map,
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int split_flag,
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int flags)
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{
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ext4_lblk_t ee_block;
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struct ext4_extent *ex;
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unsigned int ee_len, depth;
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int err = 0;
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int uninitialized;
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int split_flag1, flags1;
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depth = ext_depth(inode);
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ex = path[depth].p_ext;
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ee_block = le32_to_cpu(ex->ee_block);
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ee_len = ext4_ext_get_actual_len(ex);
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uninitialized = ext4_ext_is_uninitialized(ex);
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if (map->m_lblk + map->m_len < ee_block + ee_len) {
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split_flag1 = split_flag & EXT4_EXT_MAY_ZEROOUT ?
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EXT4_EXT_MAY_ZEROOUT : 0;
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flags1 = flags | EXT4_GET_BLOCKS_PRE_IO;
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if (uninitialized)
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split_flag1 |= EXT4_EXT_MARK_UNINIT1 |
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EXT4_EXT_MARK_UNINIT2;
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err = ext4_split_extent_at(handle, inode, path,
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map->m_lblk + map->m_len, split_flag1, flags1);
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}
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ext4_ext_drop_refs(path);
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path = ext4_ext_find_extent(inode, map->m_lblk, path);
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if (IS_ERR(path))
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return PTR_ERR(path);
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if (map->m_lblk >= ee_block) {
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split_flag1 = split_flag & EXT4_EXT_MAY_ZEROOUT ?
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EXT4_EXT_MAY_ZEROOUT : 0;
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if (uninitialized)
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split_flag1 |= EXT4_EXT_MARK_UNINIT1;
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if (split_flag & EXT4_EXT_MARK_UNINIT2)
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split_flag1 |= EXT4_EXT_MARK_UNINIT2;
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err = ext4_split_extent_at(handle, inode, path,
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map->m_lblk, split_flag1, flags);
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if (err)
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goto out;
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}
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ext4_ext_show_leaf(inode, path);
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out:
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return err ? err : map->m_len;
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}
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#define EXT4_EXT_ZERO_LEN 7
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/*
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* This function is called by ext4_ext_map_blocks() if someone tries to write
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