371 lines
7.8 KiB
C
371 lines
7.8 KiB
C
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/* Generic part */
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typedef struct {
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block_t *p;
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block_t key;
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struct buffer_head *bh;
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} Indirect;
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static DEFINE_RWLOCK(pointers_lock);
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static inline void add_chain(Indirect *p, struct buffer_head *bh, block_t *v)
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{
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p->key = *(p->p = v);
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p->bh = bh;
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}
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static inline int verify_chain(Indirect *from, Indirect *to)
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{
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while (from <= to && from->key == *from->p)
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from++;
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return (from > to);
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}
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static inline block_t *block_end(struct buffer_head *bh)
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{
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return (block_t *)((char*)bh->b_data + bh->b_size);
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}
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static inline Indirect *get_branch(struct inode *inode,
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int depth,
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int *offsets,
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Indirect chain[DEPTH],
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int *err)
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{
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struct super_block *sb = inode->i_sb;
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Indirect *p = chain;
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struct buffer_head *bh;
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*err = 0;
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/* i_data is not going away, no lock needed */
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add_chain (chain, NULL, i_data(inode) + *offsets);
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if (!p->key)
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goto no_block;
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while (--depth) {
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bh = sb_bread(sb, block_to_cpu(p->key));
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if (!bh)
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goto failure;
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read_lock(&pointers_lock);
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if (!verify_chain(chain, p))
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goto changed;
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add_chain(++p, bh, (block_t *)bh->b_data + *++offsets);
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read_unlock(&pointers_lock);
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if (!p->key)
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goto no_block;
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}
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return NULL;
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changed:
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read_unlock(&pointers_lock);
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brelse(bh);
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*err = -EAGAIN;
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goto no_block;
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failure:
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*err = -EIO;
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no_block:
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return p;
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}
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static int alloc_branch(struct inode *inode,
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int num,
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int *offsets,
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Indirect *branch)
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{
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int n = 0;
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int i;
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int parent = minix_new_block(inode);
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int err = -ENOSPC;
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branch[0].key = cpu_to_block(parent);
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if (parent) for (n = 1; n < num; n++) {
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struct buffer_head *bh;
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/* Allocate the next block */
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int nr = minix_new_block(inode);
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if (!nr)
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break;
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branch[n].key = cpu_to_block(nr);
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bh = sb_getblk(inode->i_sb, parent);
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if (!bh) {
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minix_free_block(inode, nr);
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err = -ENOMEM;
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break;
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}
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lock_buffer(bh);
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memset(bh->b_data, 0, bh->b_size);
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branch[n].bh = bh;
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branch[n].p = (block_t*) bh->b_data + offsets[n];
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*branch[n].p = branch[n].key;
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set_buffer_uptodate(bh);
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unlock_buffer(bh);
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mark_buffer_dirty_inode(bh, inode);
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parent = nr;
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}
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if (n == num)
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return 0;
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/* Allocation failed, free what we already allocated */
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for (i = 1; i < n; i++)
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bforget(branch[i].bh);
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for (i = 0; i < n; i++)
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minix_free_block(inode, block_to_cpu(branch[i].key));
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return err;
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}
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static inline int splice_branch(struct inode *inode,
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Indirect chain[DEPTH],
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Indirect *where,
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int num)
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{
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int i;
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write_lock(&pointers_lock);
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/* Verify that place we are splicing to is still there and vacant */
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if (!verify_chain(chain, where-1) || *where->p)
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goto changed;
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*where->p = where->key;
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write_unlock(&pointers_lock);
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/* We are done with atomic stuff, now do the rest of housekeeping */
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inode->i_ctime = current_time(inode);
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/* had we spliced it onto indirect block? */
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if (where->bh)
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mark_buffer_dirty_inode(where->bh, inode);
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mark_inode_dirty(inode);
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return 0;
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changed:
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write_unlock(&pointers_lock);
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for (i = 1; i < num; i++)
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bforget(where[i].bh);
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for (i = 0; i < num; i++)
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minix_free_block(inode, block_to_cpu(where[i].key));
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return -EAGAIN;
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}
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static inline int get_block(struct inode * inode, sector_t block,
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struct buffer_head *bh, int create)
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{
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int err = -EIO;
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int offsets[DEPTH];
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Indirect chain[DEPTH];
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Indirect *partial;
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int left;
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int depth = block_to_path(inode, block, offsets);
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if (depth == 0)
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goto out;
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reread:
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partial = get_branch(inode, depth, offsets, chain, &err);
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/* Simplest case - block found, no allocation needed */
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if (!partial) {
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got_it:
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map_bh(bh, inode->i_sb, block_to_cpu(chain[depth-1].key));
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/* Clean up and exit */
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partial = chain+depth-1; /* the whole chain */
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goto cleanup;
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}
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/* Next simple case - plain lookup or failed read of indirect block */
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if (!create || err == -EIO) {
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cleanup:
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while (partial > chain) {
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brelse(partial->bh);
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partial--;
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}
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out:
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return err;
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}
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/*
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* Indirect block might be removed by truncate while we were
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* reading it. Handling of that case (forget what we've got and
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* reread) is taken out of the main path.
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*/
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if (err == -EAGAIN)
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goto changed;
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left = (chain + depth) - partial;
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err = alloc_branch(inode, left, offsets+(partial-chain), partial);
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if (err)
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goto cleanup;
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if (splice_branch(inode, chain, partial, left) < 0)
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goto changed;
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set_buffer_new(bh);
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goto got_it;
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changed:
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while (partial > chain) {
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brelse(partial->bh);
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partial--;
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}
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goto reread;
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}
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static inline int all_zeroes(block_t *p, block_t *q)
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{
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while (p < q)
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if (*p++)
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return 0;
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return 1;
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}
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static Indirect *find_shared(struct inode *inode,
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int depth,
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int offsets[DEPTH],
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Indirect chain[DEPTH],
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block_t *top)
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{
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Indirect *partial, *p;
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int k, err;
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*top = 0;
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for (k = depth; k > 1 && !offsets[k-1]; k--)
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;
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partial = get_branch(inode, k, offsets, chain, &err);
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write_lock(&pointers_lock);
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if (!partial)
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partial = chain + k-1;
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if (!partial->key && *partial->p) {
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write_unlock(&pointers_lock);
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goto no_top;
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}
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for (p=partial;p>chain && all_zeroes((block_t*)p->bh->b_data,p->p);p--)
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;
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if (p == chain + k - 1 && p > chain) {
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p->p--;
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} else {
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*top = *p->p;
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*p->p = 0;
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}
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write_unlock(&pointers_lock);
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while(partial > p)
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{
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brelse(partial->bh);
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partial--;
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}
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no_top:
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return partial;
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}
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static inline void free_data(struct inode *inode, block_t *p, block_t *q)
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{
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unsigned long nr;
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for ( ; p < q ; p++) {
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nr = block_to_cpu(*p);
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if (nr) {
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*p = 0;
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minix_free_block(inode, nr);
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}
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}
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}
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static void free_branches(struct inode *inode, block_t *p, block_t *q, int depth)
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{
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struct buffer_head * bh;
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unsigned long nr;
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if (depth--) {
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for ( ; p < q ; p++) {
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nr = block_to_cpu(*p);
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if (!nr)
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continue;
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*p = 0;
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bh = sb_bread(inode->i_sb, nr);
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if (!bh)
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continue;
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free_branches(inode, (block_t*)bh->b_data,
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block_end(bh), depth);
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bforget(bh);
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minix_free_block(inode, nr);
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mark_inode_dirty(inode);
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}
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} else
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free_data(inode, p, q);
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}
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static inline void truncate (struct inode * inode)
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{
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struct super_block *sb = inode->i_sb;
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block_t *idata = i_data(inode);
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int offsets[DEPTH];
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Indirect chain[DEPTH];
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Indirect *partial;
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block_t nr = 0;
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int n;
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int first_whole;
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long iblock;
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iblock = (inode->i_size + sb->s_blocksize -1) >> sb->s_blocksize_bits;
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block_truncate_page(inode->i_mapping, inode->i_size, get_block);
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n = block_to_path(inode, iblock, offsets);
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if (!n)
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return;
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if (n == 1) {
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free_data(inode, idata+offsets[0], idata + DIRECT);
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first_whole = 0;
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goto do_indirects;
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}
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first_whole = offsets[0] + 1 - DIRECT;
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partial = find_shared(inode, n, offsets, chain, &nr);
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if (nr) {
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if (partial == chain)
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mark_inode_dirty(inode);
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else
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mark_buffer_dirty_inode(partial->bh, inode);
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free_branches(inode, &nr, &nr+1, (chain+n-1) - partial);
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}
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/* Clear the ends of indirect blocks on the shared branch */
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while (partial > chain) {
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free_branches(inode, partial->p + 1, block_end(partial->bh),
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(chain+n-1) - partial);
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mark_buffer_dirty_inode(partial->bh, inode);
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brelse (partial->bh);
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partial--;
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}
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do_indirects:
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/* Kill the remaining (whole) subtrees */
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while (first_whole < DEPTH-1) {
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nr = idata[DIRECT+first_whole];
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if (nr) {
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idata[DIRECT+first_whole] = 0;
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mark_inode_dirty(inode);
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free_branches(inode, &nr, &nr+1, first_whole+1);
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}
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first_whole++;
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}
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inode->i_mtime = inode->i_ctime = current_time(inode);
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mark_inode_dirty(inode);
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}
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static inline unsigned nblocks(loff_t size, struct super_block *sb)
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{
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int k = sb->s_blocksize_bits - 10;
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unsigned blocks, res, direct = DIRECT, i = DEPTH;
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blocks = (size + sb->s_blocksize - 1) >> (BLOCK_SIZE_BITS + k);
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res = blocks;
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while (--i && blocks > direct) {
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blocks -= direct;
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blocks += sb->s_blocksize/sizeof(block_t) - 1;
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blocks /= sb->s_blocksize/sizeof(block_t);
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res += blocks;
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direct = 1;
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}
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return res;
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}
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