diff options
| -rw-r--r-- | fs/ext3/balloc.c | 292 |
1 files changed, 247 insertions, 45 deletions
diff --git a/fs/ext3/balloc.c b/fs/ext3/balloc.c index 2bd836f..f1897fe 100644 --- a/fs/ext3/balloc.c +++ b/fs/ext3/balloc.c @@ -38,6 +38,13 @@ #define in_range(b, first, len) ((b) >= (first) && (b) <= (first) + (len) - 1) +/** + * ext3_get_group_desc() -- load group descriptor from disk + * @sb: super block + * @block_group: given block group + * @bh: pointer to the buffer head to store the block + * group descriptor + */ struct ext3_group_desc * ext3_get_group_desc(struct super_block * sb, unsigned int block_group, struct buffer_head ** bh) @@ -73,7 +80,11 @@ struct ext3_group_desc * ext3_get_group_desc(struct super_block * sb, return desc + offset; } -/* +/** + * read_block_bitmap() + * @sb: super block + * @block_group: given block group + * * Read the bitmap for a given block_group, reading into the specified * slot in the superblock's bitmap cache. * @@ -103,13 +114,20 @@ error_out: * Operations include: * dump, find, add, remove, is_empty, find_next_reservable_window, etc. * - * We use sorted double linked list for the per-filesystem reservation - * window list. (like in vm_region). + * We use a red-black tree to represent per-filesystem reservation + * windows. * - * Initially, we keep those small operations in the abstract functions, - * so later if we need a better searching tree than double linked-list, - * we could easily switch to that without changing too much - * code. + */ + +/** + * __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, @@ -161,6 +179,22 @@ restart: #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 ext3_reserve_window *rsv, ext3_grpblk_t grp_goal, unsigned int group, struct super_block * sb) @@ -179,7 +213,11 @@ goal_in_my_reservation(struct ext3_reserve_window *rsv, ext3_grpblk_t grp_goal, 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. @@ -216,6 +254,13 @@ search_reserve_window(struct rb_root *root, ext3_fsblk_t goal) return rsv; } +/** + * ext3_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 hold. + */ void ext3_rsv_window_add(struct super_block *sb, struct ext3_reserve_window_node *rsv) { @@ -246,6 +291,15 @@ void ext3_rsv_window_add(struct super_block *sb, rb_insert_color(node, root); } +/** + * ext3_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 hold. + */ static void rsv_window_remove(struct super_block *sb, struct ext3_reserve_window_node *rsv) { @@ -255,11 +309,39 @@ static void rsv_window_remove(struct super_block *sb, rb_erase(&rsv->rsv_node, &EXT3_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 EXT3_RESERVE_WINDOW_NOT_ALLOCATED. + */ static inline int rsv_is_empty(struct ext3_reserve_window *rsv) { /* a valid reservation end block could not be 0 */ - return (rsv->_rsv_end == EXT3_RESERVE_WINDOW_NOT_ALLOCATED); + return rsv->_rsv_end == EXT3_RESERVE_WINDOW_NOT_ALLOCATED; } + +/** + * ext3_init_block_alloc_info() + * @inode: file inode structure + * + * Allocate and initialize the reservation window structure, and + * link the window to the ext3 inode structure at last + * + * The reservation window structure is only dynamically allocated + * and linked to ext3 inode the first time the open file + * needs a new block. So, before every ext3_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 ext3_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 call this function. + */ void ext3_init_block_alloc_info(struct inode *inode) { struct ext3_inode_info *ei = EXT3_I(inode); @@ -289,6 +371,19 @@ void ext3_init_block_alloc_info(struct inode *inode) ei->i_block_alloc_info = block_i; } +/** + * ext3_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: + * ext3_release_file(): last writer close the file + * ext3_clear_inode(): last iput(), when nobody link to this file. + * ext3_truncate(): when the block indirect map is about to change. + * + */ void ext3_discard_reservation(struct inode *inode) { struct ext3_inode_info *ei = EXT3_I(inode); @@ -308,7 +403,14 @@ void ext3_discard_reservation(struct inode *inode) } } -/* Free given blocks, update quota and i_blocks field */ +/** + * ext3_free_blocks_sb() -- Free given blocks and update quota + * @handle: handle to this transaction + * @sb: super block + * @block: start physcial block to free + * @count: number of blocks to free + * @pdquot_freed_blocks: pointer to quota + */ void ext3_free_blocks_sb(handle_t *handle, struct super_block *sb, ext3_fsblk_t block, unsigned long count, unsigned long *pdquot_freed_blocks) @@ -492,7 +594,13 @@ error_return: return; } -/* Free given blocks, update quota and i_blocks field */ +/** + * ext3_free_blocks() -- Free given blocks and update quota + * @handle: handle for this transaction + * @inode: inode + * @block: start physical block to free + * @count: number of blocks to count + */ void ext3_free_blocks(handle_t *handle, struct inode *inode, ext3_fsblk_t block, unsigned long count) { @@ -510,7 +618,11 @@ void ext3_free_blocks(handle_t *handle, struct inode *inode, return; } -/* +/** + * ext3_test_allocatable() + * @nr: given allocation block group + * @bh: bufferhead contains the bitmap of the given block group + * * For ext3 allocations, we must not reuse any blocks which are * allocated in the bitmap buffer's "last committed data" copy. This * prevents deletes from freeing up the page for reuse until we have @@ -543,6 +655,16 @@ static int ext3_test_allocatable(ext3_grpblk_t nr, struct buffer_head *bh) return ret; } +/** + * 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 alternately through the actual + * bitmap on disk and the last-committed copy in journal, until we find a + * bit free in both bitmaps. + */ static ext3_grpblk_t bitmap_search_next_usable_block(ext3_grpblk_t start, struct buffer_head *bh, ext3_grpblk_t maxblocks) @@ -550,11 +672,6 @@ bitmap_search_next_usable_block(ext3_grpblk_t start, struct buffer_head *bh, ext3_grpblk_t next; struct journal_head *jh = bh2jh(bh); - /* - * The bitmap search --- search forward alternately through the actual - * bitmap and the last-committed copy until we find a bit free in - * both - */ while (start < maxblocks) { next = ext3_find_next_zero_bit(bh->b_data, maxblocks, start); if (next >= maxblocks) @@ -570,8 +687,14 @@ bitmap_search_next_usable_block(ext3_grpblk_t start, struct buffer_head *bh, return -1; } -/* - * Find an allocatable block in a bitmap. We honour both the bitmap and +/** + * 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 honor both the bitmap and * its last-committed copy (if that exists), and 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 @@ -622,7 +745,11 @@ find_next_usable_block(ext3_grpblk_t start, struct buffer_head *bh, return here; } -/* +/** + * claim_block() + * @block: the free block (group relative) to allocate + * @bh: the bufferhead containts the block group bitmap + * * We think we can allocate this block in this bitmap. Try to set the bit. * If that succeeds then check that nobody has allocated and then freed the * block since we saw that is was not marked in b_committed_data. If it _was_ @@ -648,7 +775,26 @@ claim_block(spinlock_t *lock, ext3_grpblk_t block, struct buffer_head *bh) return ret; } -/* +/** + * ext3_try_to_allocate() + * @sb: superblock + * @handle: handle to this transaction + * @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. In that case we must release write access to the old one via * ext3_journal_release_buffer(), else we'll run out of credits. @@ -705,7 +851,8 @@ repeat: } start = grp_goal; - if (!claim_block(sb_bgl_lock(EXT3_SB(sb), group), grp_goal, bitmap_bh)) { + if (!claim_block(sb_bgl_lock(EXT3_SB(sb), group), + grp_goal, bitmap_bh)) { /* * The block was allocated by another thread, or it was * allocated and then freed by another thread @@ -720,7 +867,8 @@ repeat: grp_goal++; while (num < *count && grp_goal < end && ext3_test_allocatable(grp_goal, bitmap_bh) - && claim_block(sb_bgl_lock(EXT3_SB(sb), group), grp_goal, bitmap_bh)) { + && claim_block(sb_bgl_lock(EXT3_SB(sb), group), + grp_goal, bitmap_bh)) { num++; grp_goal++; } @@ -931,9 +1079,10 @@ static int alloc_new_reservation(struct ext3_reserve_window_node *my_rsv, if ((my_rsv->rsv_alloc_hit > (my_rsv->rsv_end - my_rsv->rsv_start + 1) / 2)) { /* - * if we previously allocation hit ration is greater than half - * we double the size of reservation window next time - * otherwise keep the same + * 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 > EXT3_MAX_RESERVE_BLOCKS) @@ -1012,6 +1161,23 @@ retry: 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 ext3_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 ext3_new_blocks() tries to allocate blocks, + */ static void try_to_extend_reservation(struct ext3_reserve_window_node *my_rsv, struct super_block *sb, int size) { @@ -1037,7 +1203,17 @@ static void try_to_extend_reservation(struct ext3_reserve_window_node *my_rsv, spin_unlock(rsv_lock); } -/* +/** + * ext3_try_to_allocate_with_rsv() + * @sb: superblock + * @handle: handle to this transaction + * @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 + * @errp: pointer to store the error code + * * This is the main function used to allocate a new block and its reservation * window. * @@ -1053,9 +1229,7 @@ static void try_to_extend_reservation(struct ext3_reserve_window_node *my_rsv, * reservation), and there are lots of free blocks, but they are all * being reserved. * - * We use a sorted double linked list for the per-filesystem reservation list. - * The insert, remove and find a free space(non-reserved) operations for the - * sorted double linked list should be fast. + * We use a red-black tree for the per-filesystem reservation list. * */ static ext3_grpblk_t @@ -1120,7 +1294,8 @@ ext3_try_to_allocate_with_rsv(struct super_block *sb, handle_t *handle, */ while (1) { if (rsv_is_empty(&my_rsv->rsv_window) || (ret < 0) || - !goal_in_my_reservation(&my_rsv->rsv_window, grp_goal, group, sb)) { + !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, @@ -1128,19 +1303,22 @@ ext3_try_to_allocate_with_rsv(struct super_block *sb, handle_t *handle, if (ret < 0) break; /* failed */ - if (!goal_in_my_reservation(&my_rsv->rsv_window, grp_goal, group, sb)) + if (!goal_in_my_reservation(&my_rsv->rsv_window, + grp_goal, group, sb)) grp_goal = -1; - } else if (grp_goal > 0 && (my_rsv->rsv_end-grp_goal+1) < *count) + } else if (grp_goal > 0 && + (my_rsv->rsv_end-grp_goal+1) < *count) try_to_extend_reservation(my_rsv, sb, *count-my_rsv->rsv_end + grp_goal - 1); - if ((my_rsv->rsv_start >= group_first_block + EXT3_BLOCKS_PER_GROUP(sb)) + if ((my_rsv->rsv_start >= group_first_block + + EXT3_BLOCKS_PER_GROUP(sb)) || (my_rsv->rsv_end < group_first_block)) { rsv_window_dump(&EXT3_SB(sb)->s_rsv_window_root, 1); BUG(); } - ret = ext3_try_to_allocate(sb, handle, group, bitmap_bh, grp_goal, - &num, &my_rsv->rsv_window); + ret = ext3_try_to_allocate(sb, handle, group, bitmap_bh, + grp_goal, &num, &my_rsv->rsv_window); if (ret >= 0) { my_rsv->rsv_alloc_hit += num; *count = num; @@ -1165,6 +1343,12 @@ out: return ret; } +/** + * ext3_has_free_blocks() + * @sbi: in-core super block structure. + * + * Check if filesystem has at least 1 free block available for allocation. + */ static int ext3_has_free_blocks(struct ext3_sb_info *sbi) { ext3_fsblk_t free_blocks, root_blocks; @@ -1179,11 +1363,17 @@ static int ext3_has_free_blocks(struct ext3_sb_info *sbi) return 1; } -/* +/** + * ext3_should_retry_alloc() + * @sb: super block + * @retries number of attemps has been made + * * ext3_should_retry_alloc() is called when ENOSPC is returned, and if * it is profitable to retry the operation, this function will wait * for the current or commiting transaction to complete, and then * return TRUE. + * + * if the total number of retries exceed three times, return FALSE. */ int ext3_should_retry_alloc(struct super_block *sb, int *retries) { @@ -1195,13 +1385,19 @@ int ext3_should_retry_alloc(struct super_block *sb, int *retries) return journal_force_commit_nested(EXT3_SB(sb)->s_journal); } -/* - * ext3_new_block 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. +/** + * ext3_new_blocks() -- core block(s) allocation function + * @handle: handle to this transaction + * @inode: file inode + * @goal: given target block(filesystem wide) + * @count: target number of blocks to allocate + * @errp: error code + * + * ext3_new_blocks uses a goal block to assist allocation. It tries to + * allocate block(s) from the block group contains the goal block first. If that + * fails, it will try to allocate block(s) from other block groups without + * any specific goal block. + * */ ext3_fsblk_t ext3_new_blocks(handle_t *handle, struct inode *inode, ext3_fsblk_t goal, unsigned long *count, int *errp) @@ -1432,7 +1628,7 @@ allocated: spin_lock(sb_bgl_lock(sbi, group_no)); gdp->bg_free_blocks_count = - cpu_to_le16(le16_to_cpu(gdp->bg_free_blocks_count) - num); + cpu_to_le16(le16_to_cpu(gdp->bg_free_blocks_count)-num); spin_unlock(sb_bgl_lock(sbi, group_no)); percpu_counter_mod(&sbi->s_freeblocks_counter, -num); @@ -1475,6 +1671,12 @@ ext3_fsblk_t ext3_new_block(handle_t *handle, struct inode *inode, return ext3_new_blocks(handle, inode, goal, &count, errp); } +/** + * ext3_count_free_blocks() -- count filesystem free blocks + * @sb: superblock + * + * Adds up the number of free blocks from each block group. + */ ext3_fsblk_t ext3_count_free_blocks(struct super_block *sb) { ext3_fsblk_t desc_count; |
