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