/* * linux/fs/ext2/balloc.c * * Copyright (C) 1992, 1993, 1994, 1995 * Remy Card (card@masi.ibp.fr) * Laboratoire MASI - Institut Blaise Pascal * Universite Pierre et Marie Curie (Paris VI) * * Enhanced block allocation by Stephen Tweedie (sct@redhat.com), 1993 * Big-endian to little-endian byte-swapping/bitmaps by * David S. Miller (davem@caip.rutgers.edu), 1995 */ #include "ext2.h" #include #include #include #include #include /* * balloc.c contains the blocks allocation and deallocation routines */ /* * The free blocks are managed by bitmaps. A file system contains several * blocks groups. Each group contains 1 bitmap block for blocks, 1 bitmap * block for inodes, N blocks for the inode table and data blocks. * * The file system contains group descriptors which are located after the * super block. Each descriptor contains the number of the bitmap block and * the free blocks count in the block. The descriptors are loaded in memory * when a file system is mounted (see ext2_fill_super). */ #define in_range(b, first, len) ((b) >= (first) && (b) <= (first) + (len) - 1) struct ext2_group_desc * ext2_get_group_desc(struct super_block * sb, unsigned int block_group, struct buffer_head ** bh) { unsigned long group_desc; unsigned long offset; struct ext2_group_desc * desc; struct ext2_sb_info *sbi = EXT2_SB(sb); if (block_group >= sbi->s_groups_count) { ext2_error (sb, "ext2_get_group_desc", "block_group >= groups_count - " "block_group = %d, groups_count = %lu", block_group, sbi->s_groups_count); return NULL; } group_desc = block_group >> EXT2_DESC_PER_BLOCK_BITS(sb); offset = block_group & (EXT2_DESC_PER_BLOCK(sb) - 1); if (!sbi->s_group_desc[group_desc]) { ext2_error (sb, "ext2_get_group_desc", "Group descriptor not loaded - " "block_group = %d, group_desc = %lu, desc = %lu", block_group, group_desc, offset); return NULL; } desc = (struct ext2_group_desc *) sbi->s_group_desc[group_desc]->b_data; if (bh) *bh = sbi->s_group_desc[group_desc]; return desc + offset; } static int ext2_valid_block_bitmap(struct super_block *sb, struct ext2_group_desc *desc, unsigned int block_group, struct buffer_head *bh) { ext2_grpblk_t offset; ext2_grpblk_t next_zero_bit; ext2_fsblk_t bitmap_blk; ext2_fsblk_t group_first_block; group_first_block = ext2_group_first_block_no(sb, block_group); /* check whether block bitmap block number is set */ bitmap_blk = le32_to_cpu(desc->bg_block_bitmap); offset = bitmap_blk - group_first_block; if (!ext2_test_bit(offset, bh->b_data)) /* bad block bitmap */ goto err_out; /* check whether the inode bitmap block number is set */ bitmap_blk = le32_to_cpu(desc->bg_inode_bitmap); offset = bitmap_blk - group_first_block; if (!ext2_test_bit(offset, bh->b_data)) /* bad block bitmap */ goto err_out; /* check whether the inode table block number is set */ bitmap_blk = le32_to_cpu(desc->bg_inode_table); offset = bitmap_blk - group_first_block; next_zero_bit = ext2_find_next_zero_bit(bh->b_data, offset + EXT2_SB(sb)->s_itb_per_group, offset); if (next_zero_bit >= offset + EXT2_SB(sb)->s_itb_per_group) /* good bitmap for inode tables */ return 1; err_out: ext2_error(sb, __func__, "Invalid block bitmap - " "block_group = %d, block = %lu", block_group, bitmap_blk); return 0; } /* * Read the bitmap for a given block_group,and validate the * bits for block/inode/inode tables are set in the bitmaps * * Return buffer_head on success or NULL in case of failure. */ static struct buffer_head * read_block_bitmap(struct super_block *sb, unsigned int block_group) { struct ext2_group_desc * desc; struct buffer_head * bh = NULL; ext2_fsblk_t bitmap_blk; desc = ext2_get_group_desc(sb, block_group, NULL); if (!desc) return NULL; bitmap_blk = le32_to_cpu(desc->bg_block_bitmap); bh = sb_getblk(sb, bitmap_blk); if (unlikely(!bh)) { ext2_error(sb, __func__, "Cannot read block bitmap - " "block_group = %d, block_bitmap = %u", block_group, le32_to_cpu(desc->bg_block_bitmap)); return NULL; } if (likely(bh_uptodate_or_lock(bh))) return bh; if (bh_submit_read(bh) < 0) { brelse(bh); ext2_error(sb, __func__, "Cannot read block bitmap - " "block_group = %d, block_bitmap = %u", block_group, le32_to_cpu(desc->bg_block_bitmap)); return NULL; } ext2_valid_block_bitmap(sb, desc, block_group, bh); /* * file system mounted not to panic on error, continue with corrupt * bitmap */ return bh; } static void release_blocks(struct super_block *sb, int count) { if (count) { struct ext2_sb_info *sbi = EXT2_SB(sb); percpu_counter_add(&sbi->s_freeblocks_counter, count); sb->s_dirt = 1; } } static void group_adjust_blocks(struct super_block *sb, int group_no, struct ext2_group_desc *desc, struct buffer_head *bh, int count) { if (count) { struct ext2_sb_info *sbi = EXT2_SB(sb); unsigned free_blocks; spin_lock(sb_bgl_lock(sbi, group_no)); free_blocks = le16_to_cpu(desc->bg_free_blocks_count); desc->bg_free_blocks_count = cpu_to_le16(free_blocks + count); spin_unlock(sb_bgl_lock(sbi, group_no)); sb->s_dirt = 1; mark_buffer_dirty(bh); } } /* * The reservation window structure operations * -------------------------------------------- * Operations include: * dump, find, add, remove, is_empty, find_next_reservable_window, etc. * * We use a red-black tree to represent per-filesystem reservation * windows. * */ /** * __rsv_window_dump() -- Dump the filesystem block allocation reservation map * @rb_root: root of per-filesystem reservation rb tree * @verbose: verbose mode * @fn: function which wishes to dump the reservation map * * If verbose is turned on, it will print the whole block reservation * windows(start, end). Otherwise, it will only print out the "bad" windows, * those windows that overlap with their immediate neighbors. */ #if 1 static void __rsv_window_dump(struct rb_root *root, int verbose, const char *fn) { struct rb_node *n; struct ext2_reserve_window_node *rsv, *prev; int bad; restart: n = rb_first(root); bad = 0; prev = NULL; printk("Block Allocation Reservation Windows Map (%s):\n", fn); while (n) { rsv = rb_entry(n, struct ext2_reserve_window_node, rsv_node); if (verbose) printk("reservation window 0x%p " "start: %lu, end: %lu\n", rsv, rsv->rsv_start, rsv->rsv_end); if (rsv->rsv_start && rsv->rsv_start >= rsv->rsv_end) { printk("Bad reservation %p (start >= end)\n", rsv); bad = 1; } if (prev && prev->rsv_end >= rsv->rsv_start) { printk("Bad reservation %p (prev->end >= start)\n", rsv); bad = 1; } if (bad) { if (!verbose) { printk("Restarting reservation walk in verbose mode\n"); verbose = 1; goto restart; } } n = rb_next(n); prev = rsv; } printk("Window map complete.\n"); BUG_ON(bad); } #define rsv_window_dump(root, verbose) \ __rsv_window_dump((root), (verbose), __func__) #else #define rsv_window_dump(root, verbose) do {} while (0) #endif /** * goal_in_my_reservation() * @rsv: inode's reservation window * @grp_goal: given goal block relative to the allocation block group * @group: the current allocation block group * @sb: filesystem super block * * Test if the given goal block (group relative) is within the file's * own block reservation window range. * * If the reservation window is outside the goal allocation group, return 0; * grp_goal (given goal block) could be -1, which means no specific * goal block. In this case, always return 1. * If the goal block is within the reservation window, return 1; * otherwise, return 0; */ static int goal_in_my_reservation(struct ext2_reserve_window *rsv, ext2_grpblk_t grp_goal, unsigned int group, struct super_block * sb) { ext2_fsblk_t group_first_block, group_last_block; group_first_block = ext2_group_first_block_no(sb, group); group_last_block = group_first_block + EXT2_BLOCKS_PER_GROUP(sb) - 1; if ((rsv->_rsv_start > group_last_block) || (rsv->_rsv_end < group_first_block)) return 0; if ((grp_goal >= 0) && ((grp_goal + group_first_block < rsv->_rsv_start) || (grp_goal + group_first_block > rsv->_rsv_end))) return 0; return 1; } /** * search_reserve_window() * @rb_root: root of reservation tree * @goal: target allocation block * * Find the reserved window which includes the goal, or the previous one * if the goal is not in any window. * Returns NULL if there are no windows or if all windows start after the goal. */ static struct ext2_reserve_window_node * search_reserve_window(struct rb_root *root, ext2_fsblk_t goal) { struct rb_node *n = root->rb_node; struct ext2_reserve_window_node *rsv; if (!n) return NULL; do { rsv = rb_entry(n, struct ext2_reserve_window_node, rsv_node); if (goal < rsv->rsv_start) n = n->rb_left; else if (goal > rsv->rsv_end) n = n->rb_right; else return rsv; } while (n); /* * We've fallen off the end of the tree: the goal wasn't inside * any particular node. OK, the previous node must be to one * side of the interval containing the goal. If it's the RHS, * we need to back up one. */ if (rsv->rsv_start > goal) { n = rb_prev(&rsv->rsv_node); rsv = rb_entry(n, struct ext2_reserve_window_node, rsv_node); } return rsv; } /* * ext2_rsv_window_add() -- Insert a window to the block reservation rb tree. * @sb: super block * @rsv: reservation window to add * * Must be called with rsv_lock held. */ void ext2_rsv_window_add(struct super_block *sb, struct ext2_reserve_window_node *rsv) { struct rb_root *root = &EXT2_SB(sb)->s_rsv_window_root; struct rb_node *node = &rsv->rsv_node; ext2_fsblk_t start = rsv->rsv_start; struct rb_node ** p = &root->rb_node; struct rb_node * parent = NULL; struct ext2_reserve_window_node *this; while (*p) { parent = *p; this = rb_entry(parent, struct ext2_reserve_window_node, rsv_node); if (start < this->rsv_start) p = &(*p)->rb_left; else if (start > this->rsv_end) p = &(*p)->rb_right; else { rsv_window_dump(root, 1); BUG(); } } rb_link_node(node, parent, p); rb_insert_color(node, root); } /** * rsv_window_remove() -- unlink a window from the reservation rb tree * @sb: super block * @rsv: reservation window to remove * * Mark the block reservation window as not allocated, and unlink it * from the filesystem reservation window rb tree. Must be called with * rsv_lock held. */ static void rsv_window_remove(struct super_block *sb, struct ext2_reserve_window_node *rsv) { rsv->rsv_start = EXT2_RESERVE_WINDOW_NOT_ALLOCATED; rsv->rsv_end = EXT2_RESERVE_WINDOW_NOT_ALLOCATED; rsv->rsv_alloc_hit = 0; rb_erase(&rsv->rsv_node, &EXT2_SB(sb)->s_rsv_window_root); } /* * rsv_is_empty() -- Check if the reservation window is allocated. * @rsv: given reservation window to check * * returns 1 if the end block is EXT2_RESERVE_WINDOW_NOT_ALLOCATED. */ static inline int rsv_is_empty(struct ext2_reserve_window *rsv) { /* a valid reservation end block could not be 0 */ return (rsv->_rsv_end == EXT2_RESERVE_WINDOW_NOT_ALLOCATED); } /** * ext2_init_block_alloc_info() * @inode: file inode structure * * Allocate and initialize the reservation window structure, and * link the window to the ext2 inode structure at last * * The reservation window structure is only dynamically allocated * and linked to ext2 inode the first time the open file * needs a new block. So, before every ext2_new_block(s) call, for * regular files, we should check whether the reservation window * structure exists or not. In the latter case, this function is called. * Fail to do so will result in block reservation being turned off for that * open file. * * This function is called from ext2_get_blocks_handle(), also called * when setting the reservation window size through ioctl before the file * is open for write (needs block allocation). * * Needs truncate_mutex protection prior to calling this function. */ void ext2_init_block_alloc_info(struct inode *inode) { struct ext2_inode_info *ei = EXT2_I(inode); struct ext2_block_alloc_info *block_i; struct super_block *sb = inode->i_sb; block_i = kmalloc(sizeof(*block_i), GFP_NOFS); if (block_i) { struct ext2_reserve_window_node *rsv = &block_i->rsv_window_node; rsv->rsv_start = EXT2_RESERVE_WINDOW_NOT_ALLOCATED; rsv->rsv_end = EXT2_RESERVE_WINDOW_NOT_ALLOCATED; /* * if filesystem is mounted with NORESERVATION, the goal * reservation window size is set to zero to indicate * block reservation is off */ if (!test_opt(sb, RESERVATION)) rsv->rsv_goal_size = 0; else rsv->rsv_goal_size = EXT2_DEFAULT_RESERVE_BLOCKS; rsv->rsv_alloc_hit = 0; block_i->last_alloc_logical_block = 0; block_i->last_alloc_physical_block = 0; } ei->i_block_alloc_info = block_i; } /** * ext2_discard_reservation() * @inode: inode * * Discard(free) block reservation window on last file close, or truncate * or at last iput(). * * It is being called in three cases: * ext2_release_file(): last writer closes the file * ext2_clear_inode(): last iput(), when nobody links to this file. * ext2_truncate(): when the block indirect map is about to change. */ void ext2_discard_reservation(struct inode *inode) { struct ext2_inode_info *ei = EXT2_I(inode); struct ext2_block_alloc_info *block_i = ei->i_block_alloc_info; struct ext2_reserve_window_node *rsv; spinlock_t *rsv_lock = &EXT2_SB(inode->i_sb)->s_rsv_window_lock; if (!block_i) return; rsv = &block_i->rsv_window_node; if (!rsv_is_empty(&rsv->rsv_window)) { spin_lock(rsv_lock); if (!rsv_is_empty(&rsv->rsv_window)) rsv_window_remove(inode->i_sb, rsv); spin_unlock(rsv_lock); } } /** * ext2_free_blocks_sb() -- Free given blocks and update quota and i_blocks * @inode: inode * @block: start physcial block to free * @count: number of blocks to free */ void ext2_free_blocks (struct inode * inode, unsigned long block, unsigned long count) { struct buffer_head *bitmap_bh = NULL; struct buffer_head * bh2; unsigned long block_group; unsigned long bit; unsigned long i; unsigned long overflow; struct super_block * sb = inode->i_sb; struct ext2_sb_info * sbi = EXT2_SB(sb); struct ext2_group_desc * desc; struct ext2_super_block * es = sbi->s_es; unsigned freed = 0, group_freed; if (block < le32_to_cpu(es->s_first_data_block) || block + count < block || block + count > le32_to_cpu(es->s_blocks_count)) { ext2_error (sb, "ext2_free_blocks", "Freeing blocks not in datazone - " "block = %lu, count = %lu", block, count); goto error_return; } ext2_debug ("freeing block(s) %lu-%lu\n", block, block + count - 1); do_more: overflow = 0; block_group = (block - le32_to_cpu(es->s_first_data_block)) / EXT2_BLOCKS_PER_GROUP(sb); bit = (block - le32_to_cpu(es->s_first_data_block)) % EXT2_BLOCKS_PER_GROUP(sb); /* * Check to see if we are freeing blocks across a group * boundary. */ if (bit + count > EXT2_BLOCKS_PER_GROUP(sb)) { overflow = bit + count - EXT2_BLOCKS_PER_GROUP(sb); count -= overflow; } brelse(bitmap_bh); bitmap_bh = read_block_bitmap(sb, block_group); if (!bitmap_bh) goto error_return; desc = ext2_get_group_desc (sb, block_group, &bh2); if (!desc) goto error_return; if (in_range (le32_to_cpu(desc->bg_block_bitmap), block, count) || in_range (le32_to_cpu(desc->bg_inode_bitmap), block, count) || in_range (block, le32_to_cpu(desc->bg_inode_table), sbi->s_itb_per_group) || in_range (block + count - 1, le32_to_cpu(desc->bg_inode_table), sbi->s_itb_per_group)) { ext2_error (sb, "ext2_free_blocks", "Freeing blocks in system zones - " "Block = %lu, count = %lu", block, count); goto error_return; } for (i = 0, group_freed = 0; i < count; i++) { if (!ext2_clear_bit_atomic(sb_bgl_lock(sbi, block_group), bit + i, bitmap_bh->b_data)) { ext2_error(sb, __func__, "bit already cleared for block %lu", block + i); } else { group_freed++; } } mark_buffer_dirty(bitmap_bh); if (sb->s_flags & MS_SYNCHRONOUS) sync_dirty_buffer(bitmap_bh); group_adjust_blocks(sb, block_group, desc, bh2, group_freed); freed += group_freed; if (overflow) { block += count; count = overflow; goto do_more; } error_return: brelse(bitmap_bh); release_blocks(sb, freed); dquot_free_block_nodirty(inode, freed); } /** * bitmap_search_next_usable_block() * @start: the starting block (group relative) of the search * @bh: bufferhead contains the block group bitmap * @maxblocks: the ending block (group relative) of the reservation * * The bitmap search --- search forward through the actual bitmap on disk until * we find a bit free. */ static ext2_grpblk_t bitmap_search_next_usable_block(ext2_grpblk_t start, struct buffer_head *bh, ext2_grpblk_t maxblocks) { ext2_grpblk_t next; next = ext2_find_next_zero_bit(bh->b_data, maxblocks, start); if (next >= maxblocks) return -1; return next; } /** * find_next_usable_block() * @start: the starting block (group relative) to find next * allocatable block in bitmap. * @bh: bufferhead contains the block group bitmap * @maxblocks: the ending block (group relative) for the search * * Find an allocatable block in a bitmap. We perform the "most * appropriate allocation" algorithm of looking for a free block near * the initial goal; then for a free byte somewhere in the bitmap; * then for any free bit in the bitmap. */ static ext2_grpblk_t find_next_usable_block(int start, struct buffer_head *bh, int maxblocks) { ext2_grpblk_t here, next; char *p, *r; if (start > 0) { /* * The goal was occupied; search forward for a free * block within the next XX blocks. * * end_goal is more or less random, but it has to be * less than EXT2_BLOCKS_PER_GROUP. Aligning up to the * next 64-bit boundary is simple.. */ ext2_grpblk_t end_goal = (start + 63) & ~63; if (end_goal > maxblocks) end_goal = maxblocks; here = ext2_find_next_zero_bit(bh->b_data, end_goal, start); if (here < end_goal) return here; ext2_debug("Bit not found near goal\n"); } here = start; if (here < 0) here = 0; p = ((char *)bh->b_data) + (here >> 3); r = memscan(p, 0, ((maxblocks + 7) >> 3) - (here >> 3)); next = (r - ((char *)bh->b_data)) << 3; if (next < maxblocks && next >= here) return next; here = bitmap_search_next_usable_block(here, bh, maxblocks); return here; } /** * ext2_try_to_allocate() * @sb: superblock * @group: given allocation block group * @bitmap_bh: bufferhead holds the block bitmap * @grp_goal: given target block within the group * @count: target number of blocks to allocate * @my_rsv: reservation window * * Attempt to allocate blocks within a give range. Set the range of allocation * first, then find the first free bit(s) from the bitmap (within the range), * and at last, allocate the blocks by claiming the found free bit as allocated. * * To set the range of this allocation: * if there is a reservation window, only try to allocate block(s) * from the file's own reservation window; * Otherwise, the allocation range starts from the give goal block, * ends at the block group's last block. * * If we failed to allocate the desired block then we may end up crossing to a * new bitmap. */ static int ext2_try_to_allocate(struct super_block *sb, int group, struct buffer_head *bitmap_bh, ext2_grpblk_t grp_goal, unsigned long *count, struct ext2_reserve_window *my_rsv) { ext2_fsblk_t group_first_block; ext2_grpblk_t start, end; unsigned long num = 0; /* we do allocation within the reservation window if we have a window */ if (my_rsv) { group_first_block = ext2_group_first_block_no(sb, group); if (my_rsv->_rsv_start >= group_first_block) start = my_rsv->_rsv_start - group_first_block; else /* reservation window cross group boundary */ start = 0; end = my_rsv->_rsv_end - group_first_block + 1; if (end > EXT2_BLOCKS_PER_GROUP(sb)) /* reservation window crosses group boundary */ end = EXT2_BLOCKS_PER_GROUP(sb); if ((start <= grp_goal) && (grp_goal < end)) start = grp_goal; else grp_goal = -1; } else { if (grp_goal > 0) start = grp_goal; else start = 0; end = EXT2_BLOCKS_PER_GROUP(sb); } BUG_ON(start > EXT2_BLOCKS_PER_GROUP(sb)); repeat: if (grp_goal < 0) { grp_goal = find_next_usable_block(start, bitmap_bh, end); if (grp_goal < 0) goto fail_access; if (!my_rsv) { int i; for (i = 0; i < 7 && grp_goal > start && !ext2_test_bit(grp_goal - 1, bitmap_bh->b_data); i++, grp_goal--) ; } } start = grp_goal; if (ext2_set_bit_atomic(sb_bgl_lock(EXT2_SB(sb), group), grp_goal, bitmap_bh->b_data)) { /* * The block was allocated by another thread, or it was * allocated and then freed by another thread */ start++; grp_goal++; if (start >= end) goto fail_access; goto repeat; } num++; grp_goal++; while (num < *count && grp_goal < end && !ext2_set_bit_atomic(sb_bgl_lock(EXT2_SB(sb), group), grp_goal, bitmap_bh->b_data)) { num++; grp_goal++; } *count = num; return grp_goal - num; fail_access: *count = num; return -1; } /** * find_next_reservable_window(): * find a reservable space within the given range. * It does not allocate the reservation window for now: * alloc_new_reservation() will do the work later. * * @search_head: the head of the searching list; * This is not necessarily the list head of the whole filesystem * * We have both head and start_block to assist the search * for the reservable space. The list starts from head, * but we will shift to the place where start_block is, * then start from there, when looking for a reservable space. * * @size: the target new reservation window size * * @group_first_block: the first block we consider to start * the real search from * * @last_block: * the maximum block number that our goal reservable space * could start from. This is normally the last block in this * group. The search will end when we found the start of next * possible reservable space is out of this boundary. * This could handle the cross boundary reservation window * request. * * basically we search from the given range, rather than the whole * reservation double linked list, (start_block, last_block) * to find a free region that is of my size and has not * been reserved. * */ static int find_next_reservable_window( struct ext2_reserve_window_node *search_head, struct ext2_reserve_window_node *my_rsv, struct super_block * sb, ext2_fsblk_t start_block, ext2_fsblk_t last_block) { struct rb_node *next; struct ext2_reserve_window_node *rsv, *prev; ext2_fsblk_t cur; int size = my_rsv->rsv_goal_size; /* TODO: make the start of the reservation window byte-aligned */ /* cur = *start_block & ~7;*/ cur = start_block; rsv = search_head; if (!rsv) return -1; while (1) { if (cur <= rsv->rsv_end) cur = rsv->rsv_end + 1; /* TODO? * in the case we could not find a reservable space * that is what is expected, during the re-search, we could * remember what's the largest reservable space we could have * and return that one. * * For now it will fail if we could not find the reservable * space with expected-size (or more)... */ if (cur > last_block) return -1; /* fail */ prev = rsv; next = rb_next(&rsv->rsv_node); rsv = rb_entry(next,struct ext2_reserve_window_node,rsv_node); /* * Reached the last reservation, we can just append to the * previous one. */ if (!next) break; if (cur + size <= rsv->rsv_start) { /* * Found a reserveable space big enough. We could * have a reservation across the group boundary here */ break; } } /* * we come here either : * when we reach the end of the whole list, * and there is empty reservable space after last entry in the list. * append it to the end of the list. * * or we found one reservable space in the middle of the list, * return the reservation window that we could append to. * succeed. */ if ((prev != my_rsv) && (!rsv_is_empty(&my_rsv->rsv_window))) rsv_window_remove(sb, my_rsv); /* * Let's book the whole available window for now. We will check the * disk bitmap later and then, if there are free blocks then we adjust * the window size if it's larger than requested. * Otherwise, we will remove this node from the tree next time * call find_next_reservable_window. */ my_rsv->rsv_start = cur; my_rsv->rsv_end = cur + size - 1; my_rsv->rsv_alloc_hit = 0; if (prev != my_rsv) ext2_rsv_window_add(sb, my_rsv); return 0; } /** * alloc_new_reservation()--allocate a new reservation window * * To make a new reservation, we search part of the filesystem * reservation list (the list that inside the group). We try to * allocate a new reservation window near the allocation goal, * or the beginning of the group, if there is no goal. * * We first find a reservable space after the goal, then from * there, we check the bitmap for the first free block after * it. If there is no free block until the end of group, then the * whole group is full, we failed. Otherwise, check if the free * block is inside the expected reservable space, if so, we * succeed. * If the first free block is outside the reservable space, then * start from the first free block, we search for next available * space, and go on. * * on succeed, a new reservation will be found and inserted into the list * It contains at least one free block, and it does not overlap with other * reservation windows. * * failed: we failed to find a reservation window in this group * * @rsv: the reservation * * @grp_goal: The goal (group-relative). It is where the search for a * free reservable space should start from. * if we have a goal(goal >0 ), then start from there, * no goal(goal = -1), we start from the first block * of the group. * * @sb: the super block * @group: the group we are trying to allocate in * @bitmap_bh: the block group block bitmap * */ static int alloc_new_reservation(struct ext2_reserve_window_node *my_rsv, ext2_grpblk_t grp_goal, struct super_block *sb, unsigned int group, struct buffer_head *bitmap_bh) { struct ext2_reserve_window_node *search_head; ext2_fsblk_t group_first_block, group_end_block, start_block; ext2_grpblk_t first_free_block; struct rb_root *fs_rsv_root = &EXT2_SB(sb)->s_rsv_window_root; unsigned long size; int ret; spinlock_t *rsv_lock = &EXT2_SB(sb)->s_rsv_window_lock; group_first_block = ext2_group_first_block_no(sb, group); group_end_block = group_first_block + (EXT2_BLOCKS_PER_GROUP(sb) - 1); if (grp_goal < 0) start_block = group_first_block; else start_block = grp_goal + group_first_block; size = my_rsv->rsv_goal_size; if (!rsv_is_empty(&my_rsv->rsv_window)) { /* * if the old reservation is cross group boundary * and if the goal is inside the old reservation window, * we will come here when we just failed to allocate from * the first part of the window. We still have another part * that belongs to the next group. In this case, there is no * point to discard our window and try to allocate a new one * in this group(which will fail). we should * keep the reservation window, just simply move on. * * Maybe we could shift the start block of the reservation * window to the first block of next group. */ if ((my_rsv->rsv_start <= group_end_block) && (my_rsv->rsv_end > group_end_block) && (start_block >= my_rsv->rsv_start)) return -1; if ((my_rsv->rsv_alloc_hit > (my_rsv->rsv_end - my_rsv->rsv_start + 1) / 2)) { /* * if the previously allocation hit ratio is * greater than 1/2, then we double the size of * the reservation window the next time, * otherwise we keep the same size window */ size = size * 2; if (size > EXT2_MAX_RESERVE_BLOCKS) size = EXT2_MAX_RESERVE_BLOCKS; my_rsv->rsv_goal_size= size; } } spin_lock(rsv_lock); /* * shift the search start to the window near the goal block */ search_head = search_reserve_window(fs_rsv_root, start_block); /* * find_next_reservable_window() simply finds a reservable window * inside the given range(start_block, group_end_block). * * To make sure the reservation window has a free bit inside it, we * need to check the bitmap after we found a reservable window. */ retry: ret = find_next_reservable_window(search_head, my_rsv, sb, start_block, group_end_block); if (ret == -1) { if (!rsv_is_empty(&my_rsv->rsv_window)) rsv_window_remove(sb, my_rsv); spin_unlock(rsv_lock); return -1; } /* * On success, find_next_reservable_window() returns the * reservation window where there is a reservable space after it. * Before we reserve this reservable space, we need * to make sure there is at least a free block inside this region. * * Search the first free bit on the block bitmap. Search starts from * the start block of the reservable space we just found. */ spin_unlock(rsv_lock); first_free_block = bitmap_search_next_usable_block( my_rsv->rsv_start - group_first_block, bitmap_bh, group_end_block - group_first_block + 1); if (first_free_block < 0) { /* * no free block left on the bitmap, no point * to reserve the space. return failed. */ spin_lock(rsv_lock); if (!rsv_is_empty(&my_rsv->rsv_window)) rsv_window_remove(sb, my_rsv); spin_unlock(rsv_lock); return -1; /* failed */ } start_block = first_free_block + group_first_block; /* * check if the first free block is within the * free space we just reserved */ if (start_block >= my_rsv->rsv_start && start_block <= my_rsv->rsv_end) return 0; /* success */ /* * if the first free bit we found is out of the reservable space * continue search for next reservable space, * start from where the free block is, * we also shift the list head to where we stopped last time */ search_head = my_rsv; spin_lock(rsv_lock); goto retry; } /** * try_to_extend_reservation() * @my_rsv: given reservation window * @sb: super block * @size: the delta to extend * * Attempt to expand the reservation window large enough to have * required number of free blocks * * Since ext2_try_to_allocate() will always allocate blocks within * the reservation window range, if the window size is too small, * multiple blocks allocation has to stop at the end of the reservation * window. To make this more efficient, given the total number of * blocks needed and the current size of the window, we try to * expand the reservation window size if necessary on a best-effort * basis before ext2_new_blocks() tries to allocate blocks. */ static void try_to_extend_reservation(struct ext2_reserve_window_node *my_rsv, struct super_block *sb, int size) { struct ext2_reserve_window_node *next_rsv; struct rb_node *next; spinlock_t *rsv_lock = &EXT2_SB(sb)->s_rsv_window_lock; if (!spin_trylock(rsv_lock)) return; next = rb_next(&my_rsv->rsv_node); if (!next) my_rsv->rsv_end += size; else { next_rsv = rb_entry(next, struct ext2_reserve_window_node, rsv_node); if ((next_rsv->rsv_start - my_rsv->rsv_end - 1) >= size) my_rsv->rsv_end += size; else my_rsv->rsv_end = next_rsv->rsv_start - 1; } spin_unlock(rsv_lock); } /** * ext2_try_to_allocate_with_rsv() * @sb: superblock * @group: given allocation block group * @bitmap_bh: bufferhead holds the block bitmap * @grp_goal: given target block within the group * @count: target number of blocks to allocate * @my_rsv: reservation window * * This is the main function used to allocate a new block and its reservation * window. * * Each time when a new block allocation is need, first try to allocate from * its own reservation. If it does not have a reservation window, instead of * looking for a free bit on bitmap first, then look up the reservation list to * see if it is inside somebody else's reservation window, we try to allocate a * reservation window for it starting from the goal first. Then do the block * allocation within the reservation window. * * This will avoid keeping on searching the reservation list again and * again when somebody is looking for a free block (without * reservation), and there are lots of free blocks, but they are all * being reserved. * * We use a red-black tree for the per-filesystem reservation list. */ static ext2_grpblk_t ext2_try_to_allocate_with_rsv(struct super_block *sb, unsigned int group, struct buffer_head *bitmap_bh, ext2_grpblk_t grp_goal, struct ext2_reserve_window_node * my_rsv, unsigned long *count) { ext2_fsblk_t group_first_block, group_last_block; ext2_grpblk_t ret = 0; unsigned long num = *count; /* * we don't deal with reservation when * filesystem is mounted without reservation * or the file is not a regular file * or last attempt to allocate a block with reservation turned on failed */ if (my_rsv == NULL) { return ext2_try_to_allocate(sb, group, bitmap_bh, grp_goal, count, NULL); } /* * grp_goal is a group relative block number (if there is a goal) * 0 <= grp_goal < EXT2_BLOCKS_PER_GROUP(sb) * first block is a filesystem wide block number * first block is the block number of the first block in this group */ group_first_block = ext2_group_first_block_no(sb, group); group_last_block = group_first_block + (EXT2_BLOCKS_PER_GROUP(sb) - 1); /* * Basically we will allocate a new block from inode's reservation * window. * * We need to allocate a new reservation window, if: * a) inode does not have a reservation window; or * b) last attempt to allocate a block from existing reservation * failed; or * c) we come here with a goal and with a reservation window * * We do not need to allocate a new reservation window if we come here * at the beginning with a goal and the goal is inside the window, or * we don't have a goal but already have a reservation window. * then we could go to allocate from the reservation window directly. */ while (1) { if (rsv_is_empty(&my_rsv->rsv_window) || (ret < 0) || !goal_in_my_reservation(&my_rsv->rsv_window, grp_goal, group, sb)) { if (my_rsv->rsv_goal_size < *count) my_rsv->rsv_goal_size = *count; ret = alloc_new_reservation(my_rsv, grp_goal, sb, group, bitmap_bh); if (ret < 0) break; /* failed */ if (!goal_in_my_reservation(&my_rsv->rsv_window, grp_goal, group, sb)) grp_goal = -1; } else if (grp_goal >= 0) { int curr = my_rsv->rsv_end - (grp_goal + group_first_block) + 1; if (curr < *count) try_to_extend_reservation(my_rsv, sb, *count - curr); } if ((my_rsv->rsv_start > group_last_block) || (my_rsv->rsv_end < group_first_block)) { rsv_window_dump(&EXT2_SB(sb)->s_rsv_window_root, 1); BUG(); } ret = ext2_try_to_allocate(sb, group, bitmap_bh, grp_goal, &num, &my_rsv->rsv_window); if (ret >= 0) { my_rsv->rsv_alloc_hit += num; *count = num; break; /* succeed */ } num = *count; } return ret; } /** * ext2_has_free_blocks() * @sbi: in-core super block structure. * * Check if filesystem has at least 1 free block available for allocation. */ static int ext2_has_free_blocks(struct ext2_sb_info *sbi) { ext2_fsblk_t free_blocks, root_blocks; free_blocks = percpu_counter_read_positive(&sbi->s_freeblocks_counter); root_blocks = le32_to_cpu(sbi->s_es->s_r_blocks_count); if (free_blocks < root_blocks + 1 && !capable(CAP_SYS_RESOURCE) && sbi->s_resuid != current_fsuid() && (sbi->s_resgid == 0 || !in_group_p (sbi->s_resgid))) { return 0; } return 1; } /* * ext2_new_blocks() -- core block(s) allocation function * @inode: file inode * @goal: given target block(filesystem wide) * @count: target number of blocks to allocate * @errp: error code * * ext2_new_blocks uses a goal block to assist allocation. If the goal is * free, or there is a free block within 32 blocks of the goal, that block * is allocated. Otherwise a forward search is made for a free block; within * each block group the search first looks for an entire free byte in the block * bitmap, and then for any free bit if that fails. * This function also updates quota and i_blocks field. */ ext2_fsblk_t ext2_new_blocks(struct inode *inode, ext2_fsblk_t goal, unsigned long *count, int *errp) { struct buffer_head *bitmap_bh = NULL; struct buffer_head *gdp_bh; int group_no; int goal_group; ext2_grpblk_t grp_target_blk; /* blockgroup relative goal block */ ext2_grpblk_t grp_alloc_blk; /* blockgroup-relative allocated block*/ ext2_fsblk_t ret_block; /* filesyetem-wide allocated block */ int bgi; /* blockgroup iteration index */ int performed_allocation = 0; ext2_grpblk_t free_blocks; /* number of free blocks in a group */ struct super_block *sb; struct ext2_group_desc *gdp; struct ext2_super_block *es; struct ext2_sb_info *sbi; struct ext2_reserve_window_node *my_rsv = NULL; struct ext2_block_alloc_info *block_i; unsigned short windowsz = 0; unsigned long ngroups; unsigned long num = *count; int ret; *errp = -ENOSPC; sb = inode->i_sb; if (!sb) { printk("ext2_new_blocks: nonexistent device"); return 0; } /* * Check quota for allocation of this block. */ ret = dquot_alloc_block(inode, num); if (ret) { *errp = ret; return 0; } sbi = EXT2_SB(sb); es = EXT2_SB(sb)->s_es; ext2_debug("goal=%lu.\n", goal); /* * Allocate a block from reservation only when * filesystem is mounted with reservation(default,-o reservation), and * it's a regular file, and * the desired window size is greater than 0 (One could use ioctl * command EXT2_IOC_SETRSVSZ to set the window size to 0 to turn off * reservation on that particular file) */ block_i = EXT2_I(inode)->i_block_alloc_info; if (block_i) { windowsz = block_i->rsv_window_node.rsv_goal_size; if (windowsz > 0) my_rsv = &block_i->rsv_window_node; } if (!ext2_has_free_blocks(sbi)) { *errp = -ENOSPC; goto out; } /* * First, test whether the goal block is free. */ if (goal < le32_to_cpu(es->s_first_data_block) || goal >= le32_to_cpu(es->s_blocks_count)) goal = le32_to_cpu(es->s_first_data_block); group_no = (goal - le32_to_cpu(es->s_first_data_block)) / EXT2_BLOCKS_PER_GROUP(sb); goal_group = group_no; retry_alloc: gdp = ext2_get_group_desc(sb, group_no, &gdp_bh); if (!gdp) goto io_error; free_blocks = le16_to_cpu(gdp->bg_free_blocks_count); /* * if there is not enough free blocks to make a new resevation * turn off reservation for this allocation */ if (my_rsv && (free_blocks < windowsz) && (free_blocks > 0) && (rsv_is_empty(&my_rsv->rsv_window))) my_rsv = NULL; if (free_blocks > 0) { grp_target_blk = ((goal - le32_to_cpu(es->s_first_data_block)) % EXT2_BLOCKS_PER_GROUP(sb)); bitmap_bh = read_block_bitmap(sb, group_no); if (!bitmap_bh) goto io_error; grp_alloc_blk = ext2_try_to_allocate_with_rsv(sb, group_no, bitmap_bh, grp_target_blk, my_rsv, &num); if (grp_alloc_blk >= 0) goto allocated; } ngroups = EXT2_SB(sb)->s_groups_count; smp_rmb(); /* * Now search the rest of the groups. We assume that * group_no and gdp correctly point to the last group visited. */ for (bgi = 0; bgi < ngroups; bgi++) { group_no++; if (group_no >= ngroups) group_no = 0; gdp = ext2_get_group_desc(sb, group_no, &gdp_bh); if (!gdp) goto io_error; free_blocks = le16_to_cpu(gdp->bg_free_blocks_count); /* * skip this group (and avoid loading bitmap) if there * are no free blocks */ if (!free_blocks) continue; /* * skip this group if the number of * free blocks is less than half of the reservation * window size. */ if (my_rsv && (free_blocks <= (windowsz/2))) continue; brelse(bitmap_bh); bitmap_bh = read_block_bitmap(sb, group_no); if (!bitmap_bh) goto io_error; /* * try to allocate block(s) from this group, without a goal(-1). */ grp_alloc_blk = ext2_try_to_allocate_with_rsv(sb, group_no, bitmap_bh, -1, my_rsv, &num); if (grp_alloc_blk >= 0) goto allocated; } /* * We may end up a bogus earlier ENOSPC error due to * filesystem is "full" of reservations, but * there maybe indeed free blocks available on disk * In this case, we just forget about the reservations * just do block allocation as without reservations. */ if (my_rsv) { my_rsv = NULL; windowsz = 0; group_no = goal_group; goto retry_alloc; } /* No space left on the device */ *errp = -ENOSPC; goto out; allocated: ext2_debug("using block group %d(%d)\n", group_no, gdp->bg_free_blocks_count); ret_block = grp_alloc_blk + ext2_group_first_block_no(sb, group_no); if (in_range(le32_to_cpu(gdp->bg_block_bitmap), ret_block, num) || in_range(le32_to_cpu(gdp->bg_inode_bitmap), ret_block, num) || in_range(ret_block, le32_to_cpu(gdp->bg_inode_table), EXT2_SB(sb)->s_itb_per_group) || in_range(ret_block + num - 1, le32_to_cpu(gdp->bg_inode_table), EXT2_SB(sb)->s_itb_per_group)) { ext2_error(sb, "ext2_new_blocks", "Allocating block in system zone - " "blocks from "E2FSBLK", length %lu", ret_block, num); /* * ext2_try_to_allocate marked the blocks we allocated as in * use. So we may want to selectively mark some of the blocks * as free */ goto retry_alloc; } performed_allocation = 1; if (ret_block + num - 1 >= le32_to_cpu(es->s_blocks_count)) { ext2_error(sb, "ext2_new_blocks", "block("E2FSBLK") >= blocks count(%d) - " "block_group = %d, es == %p ", ret_block, le32_to_cpu(es->s_blocks_count), group_no, es); goto out; } group_adjust_blocks(sb, group_no, gdp, gdp_bh, -num); percpu_counter_sub(&sbi->s_freeblocks_counter, num); mark_buffer_dirty(bitmap_bh); if (sb->s_flags & MS_SYNCHRONOUS) sync_dirty_buffer(bitmap_bh); *errp = 0; brelse(bitmap_bh); dquot_free_block_nodirty(inode, *count-num); mark_inode_dirty(inode); *count = num; return ret_block; io_error: *errp = -EIO; out: /* * Undo the block allocation */ if (!performed_allocation) { dquot_free_block_nodirty(inode, *count); mark_inode_dirty(inode); } brelse(bitmap_bh); return 0; } ext2_fsblk_t ext2_new_block(struct inode *inode, unsigned long goal, int *errp) { unsigned long count = 1; return ext2_new_blocks(inode, goal, &count, errp); } #ifdef EXT2FS_DEBUG static const int nibblemap[] = {4, 3, 3, 2, 3, 2, 2, 1, 3, 2, 2, 1, 2, 1, 1, 0}; unsigned long ext2_count_free (struct buffer_head * map, unsigned int numchars) { unsigned int i; unsigned long sum = 0; if (!map) return (0); for (i = 0; i < numchars; i++) sum += nibblemap[map->b_data[i] & 0xf] + nibblemap[(map->b_data[i] >> 4) & 0xf]; return (sum); } #endif /* EXT2FS_DEBUG */ unsigned long ext2_count_free_blocks (struct super_block * sb) { struct ext2_group_desc * desc; unsigned long desc_count = 0; int i; #ifdef EXT2FS_DEBUG unsigned long bitmap_count, x; struct ext2_super_block *es; es = EXT2_SB(sb)->s_es; desc_count = 0; bitmap_count = 0; desc = NULL; for (i = 0; i < EXT2_SB(sb)->s_groups_count; i++) { struct buffer_head *bitmap_bh; desc = ext2_get_group_desc (sb, i, NULL); if (!desc) continue; desc_count += le16_to_cpu(desc->bg_free_blocks_count); bitmap_bh = read_block_bitmap(sb, i); if (!bitmap_bh) continue; x = ext2_count_free(bitmap_bh, sb->s_blocksize); printk ("group %d: stored = %d, counted = %lu\n", i, le16_to_cpu(desc->bg_free_blocks_count), x); bitmap_count += x; brelse(bitmap_bh); } printk("ext2_count_free_blocks: stored = %lu, computed = %lu, %lu\n", (long)le32_to_cpu(es->s_free_blocks_count), desc_count, bitmap_count); return bitmap_count; #else for (i = 0; i < EXT2_SB(sb)->s_groups_count; i++) { desc = ext2_get_group_desc (sb, i, NULL); if (!desc) continue; desc_count += le16_to_cpu(desc->bg_free_blocks_count); } return desc_count; #endif } static inline int test_root(int a, int b) { int num = b; while (a > num) num *= b; return num == a; } static int ext2_group_sparse(int group) { if (group <= 1) return 1; return (test_root(group, 3) || test_root(group, 5) || test_root(group, 7)); } /** * ext2_bg_has_super - number of blocks used by the superblock in group * @sb: superblock for filesystem * @group: group number to check * * Return the number of blocks used by the superblock (primary or backup) * in this group. Currently this will be only 0 or 1. */ int ext2_bg_has_super(struct super_block *sb, int group) { if (EXT2_HAS_RO_COMPAT_FEATURE(sb,EXT2_FEATURE_RO_COMPAT_SPARSE_SUPER)&& !ext2_group_sparse(group)) return 0; return 1; } /** * ext2_bg_num_gdb - number of blocks used by the group table in group * @sb: superblock for filesystem * @group: group number to check * * Return the number of blocks used by the group descriptor table * (primary or backup) in this group. In the future there may be a * different number of descriptor blocks in each group. */ unsigned long ext2_bg_num_gdb(struct super_block *sb, int group) { return ext2_bg_has_super(sb, group) ? EXT2_SB(sb)->s_gdb_count : 0; }