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