From: Amit Arora Date: Wed, 18 Jul 2007 01:42:38 +0000 (-0400) Subject: write support for preallocated blocks X-Git-Tag: v2.6.23-rc1~494^2~15 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=56055d3ae4cc7fa6d2b10885f20269de8a989ed7;p=linux-2.6 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 --- diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c index ba25832a75..ded3d469f9 100644 --- a/fs/ext4/extents.c +++ b/fs/ext4/extents.c @@ -1140,6 +1140,53 @@ ext4_can_extents_be_merged(struct inode *inode, struct ext4_extent *ex1, return 0; } +/* + * This function tries to merge the "ex" extent to the next extent in the tree. + * It always tries to merge towards right. If you want to merge towards + * left, pass "ex - 1" as argument instead of "ex". + * Returns 0 if the extents (ex and ex+1) were _not_ merged and returns + * 1 if they got merged. + */ +int ext4_ext_try_to_merge(struct inode *inode, + struct ext4_ext_path *path, + struct ext4_extent *ex) +{ + struct ext4_extent_header *eh; + unsigned int depth, len; + int merge_done = 0; + int uninitialized = 0; + + depth = ext_depth(inode); + BUG_ON(path[depth].p_hdr == NULL); + eh = path[depth].p_hdr; + + while (ex < EXT_LAST_EXTENT(eh)) { + if (!ext4_can_extents_be_merged(inode, ex, ex + 1)) + break; + /* merge with next extent! */ + if (ext4_ext_is_uninitialized(ex)) + uninitialized = 1; + ex->ee_len = cpu_to_le16(ext4_ext_get_actual_len(ex) + + ext4_ext_get_actual_len(ex + 1)); + if (uninitialized) + ext4_ext_mark_uninitialized(ex); + + if (ex + 1 < EXT_LAST_EXTENT(eh)) { + len = (EXT_LAST_EXTENT(eh) - ex - 1) + * sizeof(struct ext4_extent); + memmove(ex + 1, ex + 2, len); + } + eh->eh_entries = cpu_to_le16(le16_to_cpu(eh->eh_entries) - 1); + merge_done = 1; + WARN_ON(eh->eh_entries == 0); + if (!eh->eh_entries) + ext4_error(inode->i_sb, "ext4_ext_try_to_merge", + "inode#%lu, eh->eh_entries = 0!", inode->i_ino); + } + + return merge_done; +} + /* * check if a portion of the "newext" extent overlaps with an * existing extent. @@ -1328,25 +1375,7 @@ has_space: merge: /* try to merge extents to the right */ - while (nearex < EXT_LAST_EXTENT(eh)) { - if (!ext4_can_extents_be_merged(inode, nearex, nearex + 1)) - break; - /* merge with next extent! */ - if (ext4_ext_is_uninitialized(nearex)) - uninitialized = 1; - nearex->ee_len = cpu_to_le16(ext4_ext_get_actual_len(nearex) - + ext4_ext_get_actual_len(nearex + 1)); - if (uninitialized) - ext4_ext_mark_uninitialized(nearex); - - if (nearex + 1 < EXT_LAST_EXTENT(eh)) { - len = (EXT_LAST_EXTENT(eh) - nearex - 1) - * sizeof(struct ext4_extent); - memmove(nearex + 1, nearex + 2, len); - } - eh->eh_entries = cpu_to_le16(le16_to_cpu(eh->eh_entries)-1); - BUG_ON(eh->eh_entries == 0); - } + ext4_ext_try_to_merge(inode, path, nearex); /* try to merge extents to the left */ @@ -2012,15 +2041,158 @@ void ext4_ext_release(struct super_block *sb) #endif } +/* + * This function is called by ext4_ext_get_blocks() if someone tries to write + * to an uninitialized extent. It may result in splitting the uninitialized + * extent into multiple extents (upto three - one initialized and two + * uninitialized). + * There are three possibilities: + * a> There is no split required: Entire extent should be initialized + * b> Splits in two extents: Write is happening at either end of the extent + * c> Splits in three extents: Somone is writing in middle of the extent + */ +int ext4_ext_convert_to_initialized(handle_t *handle, struct inode *inode, + struct ext4_ext_path *path, + ext4_fsblk_t iblock, + unsigned long max_blocks) +{ + struct ext4_extent *ex, newex; + struct ext4_extent *ex1 = NULL; + struct ext4_extent *ex2 = NULL; + struct ext4_extent *ex3 = NULL; + struct ext4_extent_header *eh; + unsigned int allocated, ee_block, ee_len, depth; + ext4_fsblk_t newblock; + int err = 0; + int ret = 0; + + depth = ext_depth(inode); + eh = path[depth].p_hdr; + ex = path[depth].p_ext; + ee_block = le32_to_cpu(ex->ee_block); + ee_len = ext4_ext_get_actual_len(ex); + allocated = ee_len - (iblock - ee_block); + newblock = iblock - ee_block + ext_pblock(ex); + ex2 = ex; + + /* ex1: ee_block to iblock - 1 : uninitialized */ + if (iblock > ee_block) { + ex1 = ex; + ex1->ee_len = cpu_to_le16(iblock - ee_block); + ext4_ext_mark_uninitialized(ex1); + ex2 = &newex; + } + /* + * for sanity, update the length of the ex2 extent before + * we insert ex3, if ex1 is NULL. This is to avoid temporary + * overlap of blocks. + */ + if (!ex1 && allocated > max_blocks) + ex2->ee_len = cpu_to_le16(max_blocks); + /* ex3: to ee_block + ee_len : uninitialised */ + if (allocated > max_blocks) { + unsigned int newdepth; + ex3 = &newex; + ex3->ee_block = cpu_to_le32(iblock + max_blocks); + ext4_ext_store_pblock(ex3, newblock + max_blocks); + ex3->ee_len = cpu_to_le16(allocated - max_blocks); + ext4_ext_mark_uninitialized(ex3); + err = ext4_ext_insert_extent(handle, inode, path, ex3); + if (err) + goto out; + /* + * The depth, and hence eh & ex might change + * as part of the insert above. + */ + newdepth = ext_depth(inode); + if (newdepth != depth) { + depth = newdepth; + path = ext4_ext_find_extent(inode, iblock, NULL); + if (IS_ERR(path)) { + err = PTR_ERR(path); + path = NULL; + goto out; + } + eh = path[depth].p_hdr; + ex = path[depth].p_ext; + if (ex2 != &newex) + ex2 = ex; + } + allocated = max_blocks; + } + /* + * If there was a change of depth as part of the + * insertion of ex3 above, we need to update the length + * of the ex1 extent again here + */ + if (ex1 && ex1 != ex) { + ex1 = ex; + ex1->ee_len = cpu_to_le16(iblock - ee_block); + ext4_ext_mark_uninitialized(ex1); + ex2 = &newex; + } + /* ex2: iblock to iblock + maxblocks-1 : initialised */ + ex2->ee_block = cpu_to_le32(iblock); + ex2->ee_start = cpu_to_le32(newblock); + ext4_ext_store_pblock(ex2, newblock); + ex2->ee_len = cpu_to_le16(allocated); + if (ex2 != ex) + goto insert; + err = ext4_ext_get_access(handle, inode, path + depth); + if (err) + goto out; + /* + * New (initialized) extent starts from the first block + * in the current extent. i.e., ex2 == ex + * We have to see if it can be merged with the extent + * on the left. + */ + if (ex2 > EXT_FIRST_EXTENT(eh)) { + /* + * To merge left, pass "ex2 - 1" to try_to_merge(), + * since it merges towards right _only_. + */ + ret = ext4_ext_try_to_merge(inode, path, ex2 - 1); + if (ret) { + err = ext4_ext_correct_indexes(handle, inode, path); + if (err) + goto out; + depth = ext_depth(inode); + ex2--; + } + } + /* + * Try to Merge towards right. This might be required + * only when the whole extent is being written to. + * i.e. ex2 == ex and ex3 == NULL. + */ + if (!ex3) { + ret = ext4_ext_try_to_merge(inode, path, ex2); + if (ret) { + err = ext4_ext_correct_indexes(handle, inode, path); + if (err) + goto out; + } + } + /* Mark modified extent as dirty */ + err = ext4_ext_dirty(handle, inode, path + depth); + goto out; +insert: + err = ext4_ext_insert_extent(handle, inode, path, &newex); +out: + return err ? err : allocated; +} + int ext4_ext_get_blocks(handle_t *handle, struct inode *inode, ext4_fsblk_t iblock, unsigned long max_blocks, struct buffer_head *bh_result, int create, int extend_disksize) { struct ext4_ext_path *path = NULL; + struct ext4_extent_header *eh; struct ext4_extent newex, *ex; ext4_fsblk_t goal, newblock; - int err = 0, depth; + int err = 0, depth, ret; unsigned long allocated = 0; __clear_bit(BH_New, &bh_result->b_state); @@ -2033,8 +2205,10 @@ int ext4_ext_get_blocks(handle_t *handle, struct inode *inode, if (goal) { if (goal == EXT4_EXT_CACHE_GAP) { if (!create) { - /* block isn't allocated yet and - * user doesn't want to allocate it */ + /* + * block isn't allocated yet and + * user doesn't want to allocate it + */ goto out2; } /* we should allocate requested block */ @@ -2068,6 +2242,7 @@ int ext4_ext_get_blocks(handle_t *handle, struct inode *inode, * this is why assert can't be put in ext4_ext_find_extent() */ BUG_ON(path[depth].p_ext == NULL && depth != 0); + eh = path[depth].p_hdr; ex = path[depth].p_ext; if (ex) { @@ -2076,13 +2251,9 @@ int ext4_ext_get_blocks(handle_t *handle, struct inode *inode, unsigned short ee_len; /* - * Allow future support for preallocated extents to be added - * as an RO_COMPAT feature: * Uninitialized extents are treated as holes, except that - * we avoid (fail) allocating new blocks during a write. + * we split out initialized portions during a write. */ - if (le16_to_cpu(ex->ee_len) > EXT_MAX_LEN) - goto out2; ee_len = ext4_ext_get_actual_len(ex); /* if found extent covers block, simply return it */ if (iblock >= ee_block && iblock < ee_block + ee_len) { @@ -2091,12 +2262,27 @@ int ext4_ext_get_blocks(handle_t *handle, struct inode *inode, allocated = ee_len - (iblock - ee_block); ext_debug("%d fit into %lu:%d -> %llu\n", (int) iblock, ee_block, ee_len, newblock); + /* Do not put uninitialized extent in the cache */ - if (!ext4_ext_is_uninitialized(ex)) + if (!ext4_ext_is_uninitialized(ex)) { ext4_ext_put_in_cache(inode, ee_block, ee_len, ee_start, EXT4_EXT_CACHE_EXTENT); - goto out; + goto out; + } + if (create == EXT4_CREATE_UNINITIALIZED_EXT) + goto out; + if (!create) + goto out2; + + ret = ext4_ext_convert_to_initialized(handle, inode, + path, iblock, + max_blocks); + if (ret <= 0) + goto out2; + else + allocated = ret; + goto outnew; } } @@ -2105,8 +2291,10 @@ int ext4_ext_get_blocks(handle_t *handle, struct inode *inode, * we couldn't try to create block if create flag is zero */ if (!create) { - /* put just found gap into cache to speed up - * subsequent requests */ + /* + * put just found gap into cache to speed up + * subsequent requests + */ ext4_ext_put_gap_in_cache(inode, path, iblock); goto out2; } @@ -2152,6 +2340,7 @@ int ext4_ext_get_blocks(handle_t *handle, struct inode *inode, /* previous routine could use block we allocated */ newblock = ext_pblock(&newex); +outnew: __set_bit(BH_New, &bh_result->b_state); /* Cache only when it is _not_ an uninitialized extent */ @@ -2221,7 +2410,8 @@ void ext4_ext_truncate(struct inode * inode, struct page *page) err = ext4_ext_remove_space(inode, last_block); /* In a multi-transaction truncate, we only make the final - * transaction synchronous. */ + * transaction synchronous. + */ if (IS_SYNC(inode)) handle->h_sync = 1; diff --git a/include/linux/ext4_fs_extents.h b/include/linux/ext4_fs_extents.h index e3d5afc6f2..edf49ec89e 100644 --- a/include/linux/ext4_fs_extents.h +++ b/include/linux/ext4_fs_extents.h @@ -205,6 +205,9 @@ static inline int ext4_ext_get_actual_len(struct ext4_extent *ext) extern int ext4_extent_tree_init(handle_t *, struct inode *); extern int ext4_ext_calc_credits_for_insert(struct inode *, struct ext4_ext_path *); +extern int ext4_ext_try_to_merge(struct inode *inode, + struct ext4_ext_path *path, + struct ext4_extent *); extern unsigned int ext4_ext_check_overlap(struct inode *, struct ext4_extent *, struct ext4_ext_path *); extern int ext4_ext_insert_extent(handle_t *, struct inode *, struct ext4_ext_path *, struct ext4_extent *); extern int ext4_ext_walk_space(struct inode *, unsigned long, unsigned long, ext_prepare_callback, void *);