diff options
Diffstat (limited to 'fs/reiserfs/do_balan.c')
| -rw-r--r-- | fs/reiserfs/do_balan.c | 276 |
1 files changed, 154 insertions, 122 deletions
diff --git a/fs/reiserfs/do_balan.c b/fs/reiserfs/do_balan.c index 80b2b1b37169..399b2009b677 100644 --- a/fs/reiserfs/do_balan.c +++ b/fs/reiserfs/do_balan.c @@ -2,18 +2,13 @@ * Copyright 2000 by Hans Reiser, licensing governed by reiserfs/README */ -/* Now we have all buffers that must be used in balancing of the tree */ -/* Further calculations can not cause schedule(), and thus the buffer */ -/* tree will be stable until the balancing will be finished */ -/* balance the tree according to the analysis made before, */ -/* and using buffers obtained after all above. */ - -/** - ** balance_leaf_when_delete - ** balance_leaf - ** do_balance - ** - **/ +/* + * Now we have all buffers that must be used in balancing of the tree + * Further calculations can not cause schedule(), and thus the buffer + * tree will be stable until the balancing will be finished + * balance the tree according to the analysis made before, + * and using buffers obtained after all above. + */ #include <asm/uaccess.h> #include <linux/time.h> @@ -68,35 +63,39 @@ inline void do_balance_mark_leaf_dirty(struct tree_balance *tb, #define do_balance_mark_internal_dirty do_balance_mark_leaf_dirty #define do_balance_mark_sb_dirty do_balance_mark_leaf_dirty -/* summary: - if deleting something ( tb->insert_size[0] < 0 ) - return(balance_leaf_when_delete()); (flag d handled here) - else - if lnum is larger than 0 we put items into the left node - if rnum is larger than 0 we put items into the right node - if snum1 is larger than 0 we put items into the new node s1 - if snum2 is larger than 0 we put items into the new node s2 -Note that all *num* count new items being created. - -It would be easier to read balance_leaf() if each of these summary -lines was a separate procedure rather than being inlined. I think -that there are many passages here and in balance_leaf_when_delete() in -which two calls to one procedure can replace two passages, and it -might save cache space and improve software maintenance costs to do so. - -Vladimir made the perceptive comment that we should offload most of -the decision making in this function into fix_nodes/check_balance, and -then create some sort of structure in tb that says what actions should -be performed by do_balance. - --Hans */ - -/* Balance leaf node in case of delete or cut: insert_size[0] < 0 +/* + * summary: + * if deleting something ( tb->insert_size[0] < 0 ) + * return(balance_leaf_when_delete()); (flag d handled here) + * else + * if lnum is larger than 0 we put items into the left node + * if rnum is larger than 0 we put items into the right node + * if snum1 is larger than 0 we put items into the new node s1 + * if snum2 is larger than 0 we put items into the new node s2 + * Note that all *num* count new items being created. + * + * It would be easier to read balance_leaf() if each of these summary + * lines was a separate procedure rather than being inlined. I think + * that there are many passages here and in balance_leaf_when_delete() in + * which two calls to one procedure can replace two passages, and it + * might save cache space and improve software maintenance costs to do so. + * + * Vladimir made the perceptive comment that we should offload most of + * the decision making in this function into fix_nodes/check_balance, and + * then create some sort of structure in tb that says what actions should + * be performed by do_balance. + * + * -Hans + */ + +/* + * Balance leaf node in case of delete or cut: insert_size[0] < 0 * * lnum, rnum can have values >= -1 * -1 means that the neighbor must be joined with S * 0 means that nothing should be done with the neighbor - * >0 means to shift entirely or partly the specified number of items to the neighbor + * >0 means to shift entirely or partly the specified number of items + * to the neighbor */ static int balance_leaf_when_delete(struct tree_balance *tb, int flag) { @@ -149,8 +148,16 @@ static int balance_leaf_when_delete(struct tree_balance *tb, int flag) case M_CUT:{ /* cut item in S[0] */ if (is_direntry_le_ih(ih)) { - /* UFS unlink semantics are such that you can only delete one directory entry at a time. */ - /* when we cut a directory tb->insert_size[0] means number of entries to be cut (always 1) */ + /* + * UFS unlink semantics are such that you + * can only delete one directory entry at + * a time. + */ + + /* + * when we cut a directory tb->insert_size[0] + * means number of entries to be cut (always 1) + */ tb->insert_size[0] = -1; leaf_cut_from_buffer(&bi, item_pos, pos_in_item, -tb->insert_size[0]); @@ -183,13 +190,22 @@ static int balance_leaf_when_delete(struct tree_balance *tb, int flag) "UNKNOWN"), flag); } - /* the rule is that no shifting occurs unless by shifting a node can be freed */ + /* + * the rule is that no shifting occurs unless by shifting + * a node can be freed + */ n = B_NR_ITEMS(tbS0); - if (tb->lnum[0]) { /* L[0] takes part in balancing */ - if (tb->lnum[0] == -1) { /* L[0] must be joined with S[0] */ - if (tb->rnum[0] == -1) { /* R[0] must be also joined with S[0] */ + /* L[0] takes part in balancing */ + if (tb->lnum[0]) { + /* L[0] must be joined with S[0] */ + if (tb->lnum[0] == -1) { + /* R[0] must be also joined with S[0] */ + if (tb->rnum[0] == -1) { if (tb->FR[0] == PATH_H_PPARENT(tb->tb_path, 0)) { - /* all contents of all the 3 buffers will be in L[0] */ + /* + * all contents of all the 3 buffers + * will be in L[0] + */ if (PATH_H_POSITION(tb->tb_path, 1) == 0 && 1 < B_NR_ITEMS(tb->FR[0])) replace_key(tb, tb->CFL[0], @@ -208,7 +224,10 @@ static int balance_leaf_when_delete(struct tree_balance *tb, int flag) return 0; } - /* all contents of all the 3 buffers will be in R[0] */ + /* + * all contents of all the 3 buffers will + * be in R[0] + */ leaf_move_items(LEAF_FROM_S_TO_R, tb, n, -1, NULL); leaf_move_items(LEAF_FROM_L_TO_R, tb, @@ -233,7 +252,11 @@ static int balance_leaf_when_delete(struct tree_balance *tb, int flag) return 0; } - /* a part of contents of S[0] will be in L[0] and the rest part of S[0] will be in R[0] */ + + /* + * a part of contents of S[0] will be in L[0] and the + * rest part of S[0] will be in R[0] + */ RFALSE((tb->lnum[0] + tb->rnum[0] < n) || (tb->lnum[0] + tb->rnum[0] > n + 1), @@ -1178,9 +1201,7 @@ struct buffer_head *get_FEB(struct tree_balance *tb) return tb->used[i]; } -/* This is now used because reiserfs_free_block has to be able to -** schedule. -*/ +/* This is now used because reiserfs_free_block has to be able to schedule. */ static void store_thrown(struct tree_balance *tb, struct buffer_head *bh) { int i; @@ -1335,8 +1356,10 @@ static int check_before_balancing(struct tree_balance *tb) "mount point."); } - /* double check that buffers that we will modify are unlocked. (fix_nodes should already have - prepped all of these for us). */ + /* + * double check that buffers that we will modify are unlocked. + * (fix_nodes should already have prepped all of these for us). + */ if (tb->lnum[0]) { retval |= locked_or_not_in_tree(tb, tb->L[0], "L[0]"); retval |= locked_or_not_in_tree(tb, tb->FL[0], "FL[0]"); @@ -1429,49 +1452,51 @@ static void check_internal_levels(struct tree_balance *tb) #endif -/* Now we have all of the buffers that must be used in balancing of - the tree. We rely on the assumption that schedule() will not occur - while do_balance works. ( Only interrupt handlers are acceptable.) - We balance the tree according to the analysis made before this, - using buffers already obtained. For SMP support it will someday be - necessary to add ordered locking of tb. */ - -/* Some interesting rules of balancing: - - we delete a maximum of two nodes per level per balancing: we never - delete R, when we delete two of three nodes L, S, R then we move - them into R. - - we only delete L if we are deleting two nodes, if we delete only - one node we delete S - - if we shift leaves then we shift as much as we can: this is a - deliberate policy of extremism in node packing which results in - higher average utilization after repeated random balance operations - at the cost of more memory copies and more balancing as a result of - small insertions to full nodes. - - if we shift internal nodes we try to evenly balance the node - utilization, with consequent less balancing at the cost of lower - utilization. - - one could argue that the policy for directories in leaves should be - that of internal nodes, but we will wait until another day to - evaluate this.... It would be nice to someday measure and prove - these assumptions as to what is optimal.... +/* + * Now we have all of the buffers that must be used in balancing of + * the tree. We rely on the assumption that schedule() will not occur + * while do_balance works. ( Only interrupt handlers are acceptable.) + * We balance the tree according to the analysis made before this, + * using buffers already obtained. For SMP support it will someday be + * necessary to add ordered locking of tb. + */ -*/ +/* + * Some interesting rules of balancing: + * we delete a maximum of two nodes per level per balancing: we never + * delete R, when we delete two of three nodes L, S, R then we move + * them into R. + * + * we only delete L if we are deleting two nodes, if we delete only + * one node we delete S + * + * if we shift leaves then we shift as much as we can: this is a + * deliberate policy of extremism in node packing which results in + * higher average utilization after repeated random balance operations + * at the cost of more memory copies and more balancing as a result of + * small insertions to full nodes. + * + * if we shift internal nodes we try to evenly balance the node + * utilization, with consequent less balancing at the cost of lower + * utilization. + * + * one could argue that the policy for directories in leaves should be + * that of internal nodes, but we will wait until another day to + * evaluate this.... It would be nice to someday measure and prove + * these assumptions as to what is optimal.... + */ static inline void do_balance_starts(struct tree_balance *tb) { - /* use print_cur_tb() to see initial state of struct - tree_balance */ + /* use print_cur_tb() to see initial state of struct tree_balance */ /* store_print_tb (tb); */ /* do not delete, just comment it out */ -/* print_tb(flag, PATH_LAST_POSITION(tb->tb_path), tb->tb_path->pos_in_item, tb, - "check");*/ + /* + print_tb(flag, PATH_LAST_POSITION(tb->tb_path), + tb->tb_path->pos_in_item, tb, "check"); + */ RFALSE(check_before_balancing(tb), "PAP-12340: locked buffers in TB"); #ifdef CONFIG_REISERFS_CHECK REISERFS_SB(tb->tb_sb)->cur_tb = tb; @@ -1487,9 +1512,10 @@ static inline void do_balance_completed(struct tree_balance *tb) REISERFS_SB(tb->tb_sb)->cur_tb = NULL; #endif - /* reiserfs_free_block is no longer schedule safe. So, we need to - ** put the buffers we want freed on the thrown list during do_balance, - ** and then free them now + /* + * reiserfs_free_block is no longer schedule safe. So, we need to + * put the buffers we want freed on the thrown list during do_balance, + * and then free them now */ REISERFS_SB(tb->tb_sb)->s_do_balance++; @@ -1500,36 +1526,40 @@ static inline void do_balance_completed(struct tree_balance *tb) free_thrown(tb); } -void do_balance(struct tree_balance *tb, /* tree_balance structure */ - struct item_head *ih, /* item header of inserted item */ - const char *body, /* body of inserted item or bytes to paste */ - int flag) -{ /* i - insert, d - delete - c - cut, p - paste - - Cut means delete part of an item - (includes removing an entry from a - directory). - - Delete means delete whole item. - - Insert means add a new item into the - tree. - - Paste means to append to the end of an - existing file or to insert a directory - entry. */ - int child_pos, /* position of a child node in its parent */ - h; /* level of the tree being processed */ - struct item_head insert_key[2]; /* in our processing of one level - we sometimes determine what - must be inserted into the next - higher level. This insertion - consists of a key or two keys - and their corresponding - pointers */ - struct buffer_head *insert_ptr[2]; /* inserted node-ptrs for the next - level */ +/* + * do_balance - balance the tree + * + * @tb: tree_balance structure + * @ih: item header of inserted item + * @body: body of inserted item or bytes to paste + * @flag: 'i' - insert, 'd' - delete, 'c' - cut, 'p' paste + * + * Cut means delete part of an item (includes removing an entry from a + * directory). + * + * Delete means delete whole item. + * + * Insert means add a new item into the tree. + * + * Paste means to append to the end of an existing file or to + * insert a directory entry. + */ +void do_balance(struct tree_balance *tb, struct item_head *ih, + const char *body, int flag) +{ + int child_pos; /* position of a child node in its parent */ + int h; /* level of the tree being processed */ + + /* + * in our processing of one level we sometimes determine what + * must be inserted into the next higher level. This insertion + * consists of a key or two keys and their corresponding + * pointers + */ + struct item_head insert_key[2]; + + /* inserted node-ptrs for the next level */ + struct buffer_head *insert_ptr[2]; tb->tb_mode = flag; tb->need_balance_dirty = 0; @@ -1549,9 +1579,11 @@ void do_balance(struct tree_balance *tb, /* tree_balance structure */ atomic_inc(&(fs_generation(tb->tb_sb))); do_balance_starts(tb); - /* balance leaf returns 0 except if combining L R and S into - one node. see balance_internal() for explanation of this - line of code. */ + /* + * balance_leaf returns 0 except if combining L R and S into + * one node. see balance_internal() for explanation of this + * line of code. + */ child_pos = PATH_H_B_ITEM_ORDER(tb->tb_path, 0) + balance_leaf(tb, ih, body, flag, insert_key, insert_ptr); |
