write support for preallocated blocks
This patch adds write support to the uninitialized extents that get created when a preallocation is done using fallocate(). It takes care of splitting the extents into multiple (upto three) extents and merging the new split extents with neighbouring ones, if possible. Signed-off-by: Amit Arora <aarora@in.ibm.com>
This commit is contained in:
Amit Arora
Theodore Ts'o
parent
a2df2a6340
commit
56055d3ae4
2 changed files with 225 additions and 32 deletions
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@ -1140,6 +1140,53 @@ ext4_can_extents_be_merged(struct inode *inode, struct ext4_extent *ex1,
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return 0;
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}
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/*
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* This function tries to merge the "ex" extent to the next extent in the tree.
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* It always tries to merge towards right. If you want to merge towards
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* left, pass "ex - 1" as argument instead of "ex".
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* Returns 0 if the extents (ex and ex+1) were _not_ merged and returns
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* 1 if they got merged.
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*/
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int ext4_ext_try_to_merge(struct inode *inode,
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struct ext4_ext_path *path,
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struct ext4_extent *ex)
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{
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struct ext4_extent_header *eh;
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unsigned int depth, len;
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int merge_done = 0;
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int uninitialized = 0;
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depth = ext_depth(inode);
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BUG_ON(path[depth].p_hdr == NULL);
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eh = path[depth].p_hdr;
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while (ex < EXT_LAST_EXTENT(eh)) {
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if (!ext4_can_extents_be_merged(inode, ex, ex + 1))
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break;
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/* merge with next extent! */
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if (ext4_ext_is_uninitialized(ex))
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uninitialized = 1;
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ex->ee_len = cpu_to_le16(ext4_ext_get_actual_len(ex)
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+ ext4_ext_get_actual_len(ex + 1));
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if (uninitialized)
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ext4_ext_mark_uninitialized(ex);
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if (ex + 1 < EXT_LAST_EXTENT(eh)) {
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len = (EXT_LAST_EXTENT(eh) - ex - 1)
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* sizeof(struct ext4_extent);
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memmove(ex + 1, ex + 2, len);
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}
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eh->eh_entries = cpu_to_le16(le16_to_cpu(eh->eh_entries) - 1);
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merge_done = 1;
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WARN_ON(eh->eh_entries == 0);
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if (!eh->eh_entries)
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ext4_error(inode->i_sb, "ext4_ext_try_to_merge",
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"inode#%lu, eh->eh_entries = 0!", inode->i_ino);
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}
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return merge_done;
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}
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/*
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* check if a portion of the "newext" extent overlaps with an
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* existing extent.
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@ -1328,25 +1375,7 @@ has_space:
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merge:
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/* try to merge extents to the right */
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while (nearex < EXT_LAST_EXTENT(eh)) {
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if (!ext4_can_extents_be_merged(inode, nearex, nearex + 1))
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break;
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/* merge with next extent! */
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if (ext4_ext_is_uninitialized(nearex))
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uninitialized = 1;
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nearex->ee_len = cpu_to_le16(ext4_ext_get_actual_len(nearex)
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+ ext4_ext_get_actual_len(nearex + 1));
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if (uninitialized)
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ext4_ext_mark_uninitialized(nearex);
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if (nearex + 1 < EXT_LAST_EXTENT(eh)) {
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len = (EXT_LAST_EXTENT(eh) - nearex - 1)
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* sizeof(struct ext4_extent);
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memmove(nearex + 1, nearex + 2, len);
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}
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eh->eh_entries = cpu_to_le16(le16_to_cpu(eh->eh_entries)-1);
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BUG_ON(eh->eh_entries == 0);
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}
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ext4_ext_try_to_merge(inode, path, nearex);
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/* try to merge extents to the left */
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@ -2012,15 +2041,158 @@ void ext4_ext_release(struct super_block *sb)
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#endif
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}
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/*
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* This function is called by ext4_ext_get_blocks() if someone tries to write
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* to an uninitialized extent. It may result in splitting the uninitialized
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* extent into multiple extents (upto three - one initialized and two
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* uninitialized).
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* There are three possibilities:
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* a> There is no split required: Entire extent should be initialized
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* b> Splits in two extents: Write is happening at either end of the extent
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* c> Splits in three extents: Somone is writing in middle of the extent
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*/
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int ext4_ext_convert_to_initialized(handle_t *handle, struct inode *inode,
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struct ext4_ext_path *path,
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ext4_fsblk_t iblock,
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unsigned long max_blocks)
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{
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struct ext4_extent *ex, newex;
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struct ext4_extent *ex1 = NULL;
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struct ext4_extent *ex2 = NULL;
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struct ext4_extent *ex3 = NULL;
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struct ext4_extent_header *eh;
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unsigned int allocated, ee_block, ee_len, depth;
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ext4_fsblk_t newblock;
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int err = 0;
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int ret = 0;
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depth = ext_depth(inode);
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eh = path[depth].p_hdr;
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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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allocated = ee_len - (iblock - ee_block);
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newblock = iblock - ee_block + ext_pblock(ex);
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ex2 = ex;
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/* ex1: ee_block to iblock - 1 : uninitialized */
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if (iblock > ee_block) {
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ex1 = ex;
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ex1->ee_len = cpu_to_le16(iblock - ee_block);
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ext4_ext_mark_uninitialized(ex1);
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ex2 = &newex;
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}
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/*
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* for sanity, update the length of the ex2 extent before
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* we insert ex3, if ex1 is NULL. This is to avoid temporary
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* overlap of blocks.
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*/
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if (!ex1 && allocated > max_blocks)
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ex2->ee_len = cpu_to_le16(max_blocks);
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/* ex3: to ee_block + ee_len : uninitialised */
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if (allocated > max_blocks) {
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unsigned int newdepth;
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ex3 = &newex;
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ex3->ee_block = cpu_to_le32(iblock + max_blocks);
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ext4_ext_store_pblock(ex3, newblock + max_blocks);
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ex3->ee_len = cpu_to_le16(allocated - max_blocks);
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ext4_ext_mark_uninitialized(ex3);
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err = ext4_ext_insert_extent(handle, inode, path, ex3);
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if (err)
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goto out;
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/*
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* The depth, and hence eh & ex might change
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* as part of the insert above.
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*/
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newdepth = ext_depth(inode);
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if (newdepth != depth) {
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depth = newdepth;
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path = ext4_ext_find_extent(inode, iblock, NULL);
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if (IS_ERR(path)) {
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err = PTR_ERR(path);
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path = NULL;
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goto out;
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}
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eh = path[depth].p_hdr;
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ex = path[depth].p_ext;
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if (ex2 != &newex)
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ex2 = ex;
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}
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allocated = max_blocks;
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}
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/*
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* If there was a change of depth as part of the
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* insertion of ex3 above, we need to update the length
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* of the ex1 extent again here
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*/
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if (ex1 && ex1 != ex) {
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ex1 = ex;
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ex1->ee_len = cpu_to_le16(iblock - ee_block);
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ext4_ext_mark_uninitialized(ex1);
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ex2 = &newex;
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}
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/* ex2: iblock to iblock + maxblocks-1 : initialised */
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ex2->ee_block = cpu_to_le32(iblock);
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ex2->ee_start = cpu_to_le32(newblock);
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ext4_ext_store_pblock(ex2, newblock);
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ex2->ee_len = cpu_to_le16(allocated);
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if (ex2 != ex)
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goto insert;
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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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/*
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* New (initialized) extent starts from the first block
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* in the current extent. i.e., ex2 == ex
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* We have to see if it can be merged with the extent
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* on the left.
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*/
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if (ex2 > EXT_FIRST_EXTENT(eh)) {
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/*
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* To merge left, pass "ex2 - 1" to try_to_merge(),
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* since it merges towards right _only_.
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*/
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ret = ext4_ext_try_to_merge(inode, path, ex2 - 1);
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if (ret) {
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err = ext4_ext_correct_indexes(handle, inode, path);
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if (err)
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goto out;
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depth = ext_depth(inode);
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ex2--;
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}
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}
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/*
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* Try to Merge towards right. This might be required
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* only when the whole extent is being written to.
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* i.e. ex2 == ex and ex3 == NULL.
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*/
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if (!ex3) {
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ret = ext4_ext_try_to_merge(inode, path, ex2);
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if (ret) {
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err = ext4_ext_correct_indexes(handle, inode, path);
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if (err)
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goto out;
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}
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}
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/* Mark modified extent as dirty */
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err = ext4_ext_dirty(handle, inode, path + depth);
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goto out;
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insert:
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err = ext4_ext_insert_extent(handle, inode, path, &newex);
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out:
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return err ? err : allocated;
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}
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int ext4_ext_get_blocks(handle_t *handle, struct inode *inode,
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ext4_fsblk_t iblock,
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unsigned long max_blocks, struct buffer_head *bh_result,
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int create, int extend_disksize)
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{
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struct ext4_ext_path *path = NULL;
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struct ext4_extent_header *eh;
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struct ext4_extent newex, *ex;
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ext4_fsblk_t goal, newblock;
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int err = 0, depth;
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int err = 0, depth, ret;
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unsigned long allocated = 0;
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__clear_bit(BH_New, &bh_result->b_state);
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@ -2033,8 +2205,10 @@ int ext4_ext_get_blocks(handle_t *handle, struct inode *inode,
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if (goal) {
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if (goal == EXT4_EXT_CACHE_GAP) {
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if (!create) {
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/* block isn't allocated yet and
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* user doesn't want to allocate it */
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/*
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* block isn't allocated yet and
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* user doesn't want to allocate it
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*/
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goto out2;
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}
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/* we should allocate requested block */
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@ -2068,6 +2242,7 @@ int ext4_ext_get_blocks(handle_t *handle, struct inode *inode,
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* this is why assert can't be put in ext4_ext_find_extent()
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*/
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BUG_ON(path[depth].p_ext == NULL && depth != 0);
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eh = path[depth].p_hdr;
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ex = path[depth].p_ext;
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if (ex) {
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@ -2076,13 +2251,9 @@ int ext4_ext_get_blocks(handle_t *handle, struct inode *inode,
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unsigned short ee_len;
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/*
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* Allow future support for preallocated extents to be added
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* as an RO_COMPAT feature:
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* Uninitialized extents are treated as holes, except that
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* we avoid (fail) allocating new blocks during a write.
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* we split out initialized portions during a write.
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*/
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if (le16_to_cpu(ex->ee_len) > EXT_MAX_LEN)
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goto out2;
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ee_len = ext4_ext_get_actual_len(ex);
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/* if found extent covers block, simply return it */
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if (iblock >= ee_block && iblock < ee_block + ee_len) {
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@ -2091,12 +2262,27 @@ int ext4_ext_get_blocks(handle_t *handle, struct inode *inode,
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allocated = ee_len - (iblock - ee_block);
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ext_debug("%d fit into %lu:%d -> %llu\n", (int) iblock,
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ee_block, ee_len, newblock);
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/* Do not put uninitialized extent in the cache */
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if (!ext4_ext_is_uninitialized(ex))
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if (!ext4_ext_is_uninitialized(ex)) {
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ext4_ext_put_in_cache(inode, ee_block,
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ee_len, ee_start,
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EXT4_EXT_CACHE_EXTENT);
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goto out;
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goto out;
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}
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if (create == EXT4_CREATE_UNINITIALIZED_EXT)
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goto out;
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if (!create)
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goto out2;
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ret = ext4_ext_convert_to_initialized(handle, inode,
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path, iblock,
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max_blocks);
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if (ret <= 0)
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goto out2;
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else
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allocated = ret;
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goto outnew;
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}
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}
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@ -2105,8 +2291,10 @@ int ext4_ext_get_blocks(handle_t *handle, struct inode *inode,
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* we couldn't try to create block if create flag is zero
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*/
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if (!create) {
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/* put just found gap into cache to speed up
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* subsequent requests */
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/*
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* put just found gap into cache to speed up
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* subsequent requests
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*/
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ext4_ext_put_gap_in_cache(inode, path, iblock);
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goto out2;
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}
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@ -2152,6 +2340,7 @@ int ext4_ext_get_blocks(handle_t *handle, struct inode *inode,
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/* previous routine could use block we allocated */
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newblock = ext_pblock(&newex);
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outnew:
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__set_bit(BH_New, &bh_result->b_state);
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/* Cache only when it is _not_ an uninitialized extent */
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@ -2221,7 +2410,8 @@ void ext4_ext_truncate(struct inode * inode, struct page *page)
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err = ext4_ext_remove_space(inode, last_block);
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/* In a multi-transaction truncate, we only make the final
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* transaction synchronous. */
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* transaction synchronous.
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*/
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if (IS_SYNC(inode))
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handle->h_sync = 1;
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@ -205,6 +205,9 @@ static inline int ext4_ext_get_actual_len(struct ext4_extent *ext)
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extern int ext4_extent_tree_init(handle_t *, struct inode *);
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extern int ext4_ext_calc_credits_for_insert(struct inode *, struct ext4_ext_path *);
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extern int ext4_ext_try_to_merge(struct inode *inode,
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struct ext4_ext_path *path,
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struct ext4_extent *);
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extern unsigned int ext4_ext_check_overlap(struct inode *, struct ext4_extent *, struct ext4_ext_path *);
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extern int ext4_ext_insert_extent(handle_t *, struct inode *, struct ext4_ext_path *, struct ext4_extent *);
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extern int ext4_ext_walk_space(struct inode *, unsigned long, unsigned long, ext_prepare_callback, void *);
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