Viewing file:  itree_common.c (7.17 KB) -rw-r--r--
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/* Generic part */
typedef struct {
block_t *p;
block_t key;
struct buffer_head *bh;
} Indirect;
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;
/* Reader: pointers */
if (!verify_chain(chain, p))
goto changed;
add_chain(++p, bh, (block_t *)bh->b_data + *++offsets);
/* Reader: end */
if (!p->key)
goto no_block;
}
return NULL;
changed:
*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;
mark_buffer_uptodate(bh, 1);
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;
/* Verify that place we are splicing to is still there and vacant */
/* Writer: pointers */
if (!verify_chain(chain, where-1) || *where->p)
/* Writer: end */
goto changed;
/* That's it */
*where->p = where->key;
/* Writer: end */
/* We are done with atomic stuff, now do the rest of housekeeping */
inode->i_ctime = CURRENT_TIME;
/* had we spliced it onto indirect block? */
if (where->bh)
mark_buffer_dirty_inode(where->bh, inode);
mark_inode_dirty(inode);
return 0;
changed:
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, long block,
struct buffer_head *bh_result, 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;
lock_kernel();
reread:
partial = get_branch(inode, depth, offsets, chain, &err);
/* Simplest case - block found, no allocation needed */
if (!partial) {
got_it:
bh_result->b_dev = inode->i_dev;
bh_result->b_blocknr = block_to_cpu(chain[depth-1].key);
bh_result->b_state |= (1UL << BH_Mapped);
/* 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--;
}
unlock_kernel();
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;
bh_result->b_state |= (1UL << BH_New);
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);
/* Writer: pointers */
if (!partial)
partial = chain + k-1;
if (!partial->key && *partial->p)
/* Writer: end */
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;
}
/* Writer: end */
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;
mark_inode_dirty(inode);
}
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