1 files changed, 362 insertions, 0 deletions

diff --git a/fs/minix/itree_common.c b/fs/minix/itree_common.c
new file mode 100644
index 000000000000..429baf8de105
--- /dev/null
+++ b/fs/minix/itree_common.c
@@ -0,0 +1,362 @@
+/* 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 + BLOCK_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, BLOCK_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)
+{
+        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 + BLOCK_SIZE-1) >> 10;
+        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)
+{
+        unsigned blocks, res, direct = DIRECT, i = DEPTH;
+        blocks = (size + BLOCK_SIZE - 1) >> BLOCK_SIZE_BITS;
+        res = blocks;
+        while (--i && blocks > direct) {
+                blocks -= direct;
+                blocks += BLOCK_SIZE/sizeof(block_t) - 1;
+                blocks /= BLOCK_SIZE/sizeof(block_t);
+                res += blocks;
+                direct = 1;
+        }
+        return res;
+}