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503 lines
12 KiB
503 lines
12 KiB
// SPDX-License-Identifier: GPL-2.0 |
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/* |
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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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|
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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(inode); |
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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(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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} |
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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 user_namespace *mnt_userns, const struct path *path, |
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struct kstat *stat, u32 request_mask, unsigned int flags) |
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{ |
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struct super_block *s = path->dentry->d_sb; |
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generic_fillattr(&init_user_ns, d_inode(path->dentry), 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 void sysv_write_failed(struct address_space *mapping, loff_t to) |
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{ |
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struct inode *inode = mapping->host; |
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if (to > inode->i_size) { |
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truncate_pagecache(inode, inode->i_size); |
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sysv_truncate(inode); |
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} |
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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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sysv_write_failed(mapping, pos + len); |
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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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