--- /dev/null
+/*
+ * linux/fs/sysv/itree.c
+ *
+ * Handling of indirect blocks' trees.
+ * AV, Sep--Dec 2000
+ */
+
+#include <linux/buffer_head.h>
+#include <linux/mount.h>
+#include <linux/string.h>
+#include "sysv.h"
+
+enum {DIRECT = 10, DEPTH = 4}; /* Have triple indirect */
+
+static inline void dirty_indirect(struct buffer_head *bh, struct inode *inode)
+{
+ mark_buffer_dirty_inode(bh, inode);
+ if (IS_SYNC(inode))
+ sync_dirty_buffer(bh);
+}
+
+static int block_to_path(struct inode *inode, long block, int offsets[DEPTH])
+{
+ struct super_block *sb = inode->i_sb;
+ struct sysv_sb_info *sbi = SYSV_SB(sb);
+ int ptrs_bits = sbi->s_ind_per_block_bits;
+ unsigned long indirect_blocks = sbi->s_ind_per_block,
+ double_blocks = sbi->s_ind_per_block_2;
+ int n = 0;
+
+ if (block < 0) {
+ printk("sysv_block_map: block < 0\n");
+ } else if (block < DIRECT) {
+ offsets[n++] = block;
+ } else if ( (block -= DIRECT) < indirect_blocks) {
+ offsets[n++] = DIRECT;
+ offsets[n++] = block;
+ } else if ((block -= indirect_blocks) < double_blocks) {
+ offsets[n++] = DIRECT+1;
+ offsets[n++] = block >> ptrs_bits;
+ offsets[n++] = block & (indirect_blocks - 1);
+ } else if (((block -= double_blocks) >> (ptrs_bits * 2)) < indirect_blocks) {
+ offsets[n++] = DIRECT+2;
+ offsets[n++] = block >> (ptrs_bits * 2);
+ offsets[n++] = (block >> ptrs_bits) & (indirect_blocks - 1);
+ offsets[n++] = block & (indirect_blocks - 1);
+ } else {
+ /* nothing */;
+ }
+ return n;
+}
+
+static inline int block_to_cpu(struct sysv_sb_info *sbi, sysv_zone_t nr)
+{
+ return sbi->s_block_base + fs32_to_cpu(sbi, nr);
+}
+
+typedef struct {
+ sysv_zone_t *p;
+ sysv_zone_t key;
+ struct buffer_head *bh;
+} Indirect;
+
+static DEFINE_RWLOCK(pointers_lock);
+
+static inline void add_chain(Indirect *p, struct buffer_head *bh, sysv_zone_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 sysv_zone_t *block_end(struct buffer_head *bh)
+{
+ return (sysv_zone_t*)((char*)bh->b_data + bh->b_size);
+}
+
+/*
+ * Requires read_lock(&pointers_lock) or write_lock(&pointers_lock)
+ */
+static Indirect *get_branch(struct inode *inode,
+ int depth,
+ int offsets[],
+ Indirect chain[],
+ int *err)
+{
+ struct super_block *sb = inode->i_sb;
+ Indirect *p = chain;
+ struct buffer_head *bh;
+
+ *err = 0;
+ add_chain(chain, NULL, SYSV_I(inode)->i_data + *offsets);
+ if (!p->key)
+ goto no_block;
+ while (--depth) {
+ int block = block_to_cpu(SYSV_SB(sb), p->key);
+ bh = sb_bread(sb, block);
+ if (!bh)
+ goto failure;
+ if (!verify_chain(chain, p))
+ goto changed;
+ add_chain(++p, bh, (sysv_zone_t*)bh->b_data + *++offsets);
+ if (!p->key)
+ goto no_block;
+ }
+ return NULL;
+
+changed:
+ 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 blocksize = inode->i_sb->s_blocksize;
+ int n = 0;
+ int i;
+
+ branch[0].key = sysv_new_block(inode->i_sb);
+ if (branch[0].key) for (n = 1; n < num; n++) {
+ struct buffer_head *bh;
+ int parent;
+ /* Allocate the next block */
+ branch[n].key = sysv_new_block(inode->i_sb);
+ if (!branch[n].key)
+ break;
+ /*
+ * Get buffer_head for parent block, zero it out and set
+ * the pointer to new one, then send parent to disk.
+ */
+ parent = block_to_cpu(SYSV_SB(inode->i_sb), branch[n-1].key);
+ bh = sb_getblk(inode->i_sb, parent);
+ lock_buffer(bh);
+ memset(bh->b_data, 0, blocksize);
+ branch[n].bh = bh;
+ branch[n].p = (sysv_zone_t*) bh->b_data + offsets[n];
+ *branch[n].p = branch[n].key;
+ set_buffer_uptodate(bh);
+ unlock_buffer(bh);
+ dirty_indirect(bh, inode);
+ }
+ 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++)
+ sysv_free_block(inode->i_sb, branch[i].key);
+ return -ENOSPC;
+}
+
+static inline int splice_branch(struct inode *inode,
+ Indirect chain[],
+ Indirect *where,
+ int num)
+{
+ int i;
+
+ /* Verify that place we are splicing to is still there and vacant */
+ write_lock(&pointers_lock);
+ if (!verify_chain(chain, where-1) || *where->p)
+ goto changed;
+ *where->p = where->key;
+ write_unlock(&pointers_lock);
+
+ inode->i_ctime = CURRENT_TIME_SEC;
+
+ /* had we spliced it onto indirect block? */
+ if (where->bh)
+ dirty_indirect(where->bh, inode);
+
+ if (IS_SYNC(inode))
+ sysv_sync_inode(inode);
+ else
+ 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++)
+ sysv_free_block(inode->i_sb, where[i].key);
+ return -EAGAIN;
+}
+
+static int get_block(struct inode *inode, sector_t iblock, struct buffer_head *bh_result, int create)
+{
+ int err = -EIO;
+ int offsets[DEPTH];
+ Indirect chain[DEPTH];
+ struct super_block *sb = inode->i_sb;
+ Indirect *partial;
+ int left;
+ int depth = block_to_path(inode, iblock, offsets);
+
+ if (depth == 0)
+ goto out;
+
+reread:
+ read_lock(&pointers_lock);
+ partial = get_branch(inode, depth, offsets, chain, &err);
+ read_unlock(&pointers_lock);
+
+ /* Simplest case - block found, no allocation needed */
+ if (!partial) {
+got_it:
+ map_bh(bh_result, sb, block_to_cpu(SYSV_SB(sb),
+ 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_result);
+ goto got_it;
+
+changed:
+ while (partial > chain) {
+ brelse(partial->bh);
+ partial--;
+ }
+ goto reread;
+}
+
+static inline int all_zeroes(sysv_zone_t *p, sysv_zone_t *q)
+{
+ while (p < q)
+ if (*p++)
+ return 0;
+ return 1;
+}
+
+static Indirect *find_shared(struct inode *inode,
+ int depth,
+ int offsets[],
+ Indirect chain[],
+ sysv_zone_t *top)
+{
+ Indirect *partial, *p;
+ int k, err;
+
+ *top = 0;
+ for (k = depth; k > 1 && !offsets[k-1]; k--)
+ ;
+
+ write_lock(&pointers_lock);
+ partial = get_branch(inode, k, offsets, chain, &err);
+ if (!partial)
+ partial = chain + k-1;
+ /*
+ * If the branch acquired continuation since we've looked at it -
+ * fine, it should all survive and (new) top doesn't belong to us.
+ */
+ if (!partial->key && *partial->p) {
+ write_unlock(&pointers_lock);
+ goto no_top;
+ }
+ for (p=partial; p>chain && all_zeroes((sysv_zone_t*)p->bh->b_data,p->p); p--)
+ ;
+ /*
+ * OK, we've found the last block that must survive. The rest of our
+ * branch should be detached before unlocking. However, if that rest
+ * of branch is all ours and does not grow immediately from the inode
+ * it's easier to cheat and just decrement partial->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, sysv_zone_t *p, sysv_zone_t *q)
+{
+ for ( ; p < q ; p++) {
+ sysv_zone_t nr = *p;
+ if (nr) {
+ *p = 0;
+ sysv_free_block(inode->i_sb, nr);
+ mark_inode_dirty(inode);
+ }
+ }
+}
+
+static void free_branches(struct inode *inode, sysv_zone_t *p, sysv_zone_t *q, int depth)
+{
+ struct buffer_head * bh;
+ struct super_block *sb = inode->i_sb;
+
+ if (depth--) {
+ for ( ; p < q ; p++) {
+ int block;
+ sysv_zone_t nr = *p;
+ if (!nr)
+ continue;
+ *p = 0;
+ block = block_to_cpu(SYSV_SB(sb), nr);
+ bh = sb_bread(sb, block);
+ if (!bh)
+ continue;
+ free_branches(inode, (sysv_zone_t*)bh->b_data,
+ block_end(bh), depth);
+ bforget(bh);
+ sysv_free_block(sb, nr);
+ mark_inode_dirty(inode);
+ }
+ } else
+ free_data(inode, p, q);
+}
+
+void sysv_truncate (struct inode * inode)
+{
+ sysv_zone_t *i_data = SYSV_I(inode)->i_data;
+ int offsets[DEPTH];
+ Indirect chain[DEPTH];
+ Indirect *partial;
+ sysv_zone_t nr = 0;
+ int n;
+ long iblock;
+ unsigned blocksize;
+
+ if (!(S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode) ||
+ S_ISLNK(inode->i_mode)))
+ return;
+
+ blocksize = inode->i_sb->s_blocksize;
+ iblock = (inode->i_size + blocksize-1)
+ >> inode->i_sb->s_blocksize_bits;
+
+ block_truncate_page(inode->i_mapping, inode->i_size, get_block);
+
+ n = block_to_path(inode, iblock, offsets);
+ if (n == 0)
+ return;
+
+ if (n == 1) {
+ free_data(inode, i_data+offsets[0], i_data + DIRECT);
+ goto do_indirects;
+ }
+
+ partial = find_shared(inode, n, offsets, chain, &nr);
+ /* Kill the top of shared branch (already detached) */
+ if (nr) {
+ if (partial == chain)
+ mark_inode_dirty(inode);
+ else
+ dirty_indirect(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);
+ dirty_indirect(partial->bh, inode);
+ brelse (partial->bh);
+ partial--;
+ }
+do_indirects:
+ /* Kill the remaining (whole) subtrees (== subtrees deeper than...) */
+ while (n < DEPTH) {
+ nr = i_data[DIRECT + n - 1];
+ if (nr) {
+ i_data[DIRECT + n - 1] = 0;
+ mark_inode_dirty(inode);
+ free_branches(inode, &nr, &nr+1, n);
+ }
+ n++;
+ }
+ inode->i_mtime = inode->i_ctime = CURRENT_TIME_SEC;
+ if (IS_SYNC(inode))
+ sysv_sync_inode (inode);
+ else
+ mark_inode_dirty(inode);
+}
+
+static unsigned sysv_nblocks(struct super_block *s, loff_t size)
+{
+ struct sysv_sb_info *sbi = SYSV_SB(s);
+ int ptrs_bits = sbi->s_ind_per_block_bits;
+ unsigned blocks, res, direct = DIRECT, i = DEPTH;
+ blocks = (size + s->s_blocksize - 1) >> s->s_blocksize_bits;
+ res = blocks;
+ while (--i && blocks > direct) {
+ blocks = ((blocks - direct - 1) >> ptrs_bits) + 1;
+ res += blocks;
+ direct = 1;
+ }
+ return blocks;
+}
+
+int sysv_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat)
+{
+ struct super_block *s = dentry->d_sb;
+ generic_fillattr(d_inode(dentry), stat);
+ stat->blocks = (s->s_blocksize / 512) * sysv_nblocks(s, stat->size);
+ stat->blksize = s->s_blocksize;
+ return 0;
+}
+
+static int sysv_writepage(struct page *page, struct writeback_control *wbc)
+{
+ return block_write_full_page(page,get_block,wbc);
+}
+
+static int sysv_readpage(struct file *file, struct page *page)
+{
+ return block_read_full_page(page,get_block);
+}
+
+int sysv_prepare_chunk(struct page *page, loff_t pos, unsigned len)
+{
+ return __block_write_begin(page, pos, len, get_block);
+}
+
+static void sysv_write_failed(struct address_space *mapping, loff_t to)
+{
+ struct inode *inode = mapping->host;
+
+ if (to > inode->i_size) {
+ truncate_pagecache(inode, inode->i_size);
+ sysv_truncate(inode);
+ }
+}
+
+static int sysv_write_begin(struct file *file, struct address_space *mapping,
+ loff_t pos, unsigned len, unsigned flags,
+ struct page **pagep, void **fsdata)
+{
+ int ret;
+
+ ret = block_write_begin(mapping, pos, len, flags, pagep, get_block);
+ if (unlikely(ret))
+ sysv_write_failed(mapping, pos + len);
+
+ return ret;
+}
+
+static sector_t sysv_bmap(struct address_space *mapping, sector_t block)
+{
+ return generic_block_bmap(mapping,block,get_block);
+}
+
+const struct address_space_operations sysv_aops = {
+ .readpage = sysv_readpage,
+ .writepage = sysv_writepage,
+ .write_begin = sysv_write_begin,
+ .write_end = generic_write_end,
+ .bmap = sysv_bmap
+};
Code Review / kvmfornfv.git / blobdiff