file.c

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/*
 *  linux/fs/affs/file.c
 *
 *  (c) 1996  Hans-Joachim Widmaier - Rewritten
 *
 *  (C) 1993  Ray Burr - Modified for Amiga FFS filesystem.
 *
 *  (C) 1992  Eric Youngdale Modified for ISO 9660 filesystem.
 *
 *  (C) 1991  Linus Torvalds - minix filesystem
 *
 *  affs regular file handling primitives
 */

#include <asm/div64.h>
#include <asm/uaccess.h>
#include <asm/system.h>
#include <linux/sched.h>
#include <linux/affs_fs.h>
#include <linux/fcntl.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/slab.h>
#include <linux/stat.h>
#include <linux/locks.h>
#include <linux/smp_lock.h>
#include <linux/dirent.h>
#include <linux/fs.h>
#include <linux/amigaffs.h>
#include <linux/mm.h>
#include <linux/pagemap.h>

#if PAGE_SIZE < 4096
#error PAGE_SIZE must be at least 4096
#endif

static int affs_grow_extcache(struct inode *inode, u32 lc_idx);
static struct buffer_head *affs_alloc_extblock(struct inode *inode, struct buffer_head *bh, u32 ext);
static inline struct buffer_head *affs_get_extblock(struct inode *inode, u32 ext);
static struct buffer_head *affs_get_extblock_slow(struct inode *inode, u32 ext);
static int affs_get_block(struct inode *inode, long block, struct buffer_head *bh_result, int create);

static ssize_t affs_file_write(struct file *filp, const char *buf, size_t count, loff_t *ppos);
static int affs_file_open(struct inode *inode, struct file *filp);
static int affs_file_release(struct inode *inode, struct file *filp);

struct file_operations affs_file_operations = {
	llseek:		generic_file_llseek,
	read:		generic_file_read,
	write:		affs_file_write,
	mmap:		generic_file_mmap,
	open:		affs_file_open,
	release:	affs_file_release,
	fsync:		file_fsync,
};

struct inode_operations affs_file_inode_operations = {
	truncate:	affs_truncate,
	setattr:	affs_notify_change,
};

static int
affs_file_open(struct inode *inode, struct file *filp)
{
	if (atomic_read(&filp->f_count) != 1)
		return 0;
	pr_debug("AFFS: open(%d)\n", AFFS_INODE->i_opencnt);
	AFFS_INODE->i_opencnt++;
	return 0;
}

static int
affs_file_release(struct inode *inode, struct file *filp)
{
	if (atomic_read(&filp->f_count) != 0)
		return 0;
	pr_debug("AFFS: release(%d)\n", AFFS_INODE->i_opencnt);
	AFFS_INODE->i_opencnt--;
	if (!AFFS_INODE->i_opencnt)
		affs_free_prealloc(inode);

	return 0;
}

static int
affs_grow_extcache(struct inode *inode, u32 lc_idx)
{
	struct super_block	*sb = inode->i_sb;
	struct buffer_head	*bh;
	u32 lc_max;
	int i, j, key;

	if (!AFFS_INODE->i_lc) {
		char *ptr = (char *)get_zeroed_page(GFP_NOFS);
		if (!ptr)
			return -ENOMEM;
		AFFS_INODE->i_lc = (u32 *)ptr;
		AFFS_INODE->i_ac = (struct affs_ext_key *)(ptr + AFFS_CACHE_SIZE / 2);
	}

	lc_max = AFFS_LC_SIZE << AFFS_INODE->i_lc_shift;

	if (AFFS_INODE->i_extcnt > lc_max) {
		u32 lc_shift, lc_mask, tmp, off;

		/* need to recalculate linear cache, start from old size */
		lc_shift = AFFS_INODE->i_lc_shift;
		tmp = (AFFS_INODE->i_extcnt / AFFS_LC_SIZE) >> lc_shift;
		for (; tmp; tmp >>= 1)
			lc_shift++;
		lc_mask = (1 << lc_shift) - 1;

		/* fix idx and old size to new shift */
		lc_idx >>= (lc_shift - AFFS_INODE->i_lc_shift);
		AFFS_INODE->i_lc_size >>= (lc_shift - AFFS_INODE->i_lc_shift);

		/* first shrink old cache to make more space */
		off = 1 << (lc_shift - AFFS_INODE->i_lc_shift);
		for (i = 1, j = off; j < AFFS_LC_SIZE; i++, j += off)
			AFFS_INODE->i_ac[i] = AFFS_INODE->i_ac[j];

		AFFS_INODE->i_lc_shift = lc_shift;
		AFFS_INODE->i_lc_mask = lc_mask;
	}

	/* fill cache to the needed index */
	i = AFFS_INODE->i_lc_size;
	AFFS_INODE->i_lc_size = lc_idx + 1;
	for (; i <= lc_idx; i++) {
		if (!i) {
			AFFS_INODE->i_lc[0] = inode->i_ino;
			continue;
		}
		key = AFFS_INODE->i_lc[i - 1];
		j = AFFS_INODE->i_lc_mask + 1;
		// unlock cache
		for (; j > 0; j--) {
			bh = affs_bread(sb, key);
			if (!bh)
				goto err;
			key = be32_to_cpu(AFFS_TAIL(sb, bh)->extension);
			affs_brelse(bh);
		}
		// lock cache
		AFFS_INODE->i_lc[i] = key;
	}

	return 0;

err:
	// lock cache
	return -EIO;
}

static struct buffer_head *
affs_alloc_extblock(struct inode *inode, struct buffer_head *bh, u32 ext)
{
	struct super_block *sb = inode->i_sb;
	struct buffer_head *new_bh;
	u32 blocknr, tmp;

	blocknr = affs_alloc_block(inode, bh->b_blocknr);
	if (!blocknr)
		return ERR_PTR(-ENOSPC);

	new_bh = affs_getzeroblk(sb, blocknr);
	if (!new_bh) {
		affs_free_block(sb, blocknr);
		return ERR_PTR(-EIO);
	}

	AFFS_HEAD(new_bh)->ptype = cpu_to_be32(T_LIST);
	AFFS_HEAD(new_bh)->key = cpu_to_be32(blocknr);
	AFFS_TAIL(sb, new_bh)->stype = cpu_to_be32(ST_FILE);
	AFFS_TAIL(sb, new_bh)->parent = cpu_to_be32(inode->i_ino);
	affs_fix_checksum(sb, new_bh);

	mark_buffer_dirty_inode(new_bh, inode);

	tmp = be32_to_cpu(AFFS_TAIL(sb, bh)->extension);
	if (tmp)
		affs_warning(sb, "alloc_ext", "previous extension set (%x)", tmp);
	AFFS_TAIL(sb, bh)->extension = cpu_to_be32(blocknr);
	affs_adjust_checksum(bh, blocknr - tmp);
	mark_buffer_dirty_inode(bh, inode);

	AFFS_INODE->i_extcnt++;
	mark_inode_dirty(inode);

	return new_bh;
}

static inline struct buffer_head *
affs_get_extblock(struct inode *inode, u32 ext)
{
	/* inline the simplest case: same extended block as last time */
	struct buffer_head *bh = AFFS_INODE->i_ext_bh;
	if (ext == AFFS_INODE->i_ext_last)
		atomic_inc(&bh->b_count);
	else
		/* we have to do more (not inlined) */
		bh = affs_get_extblock_slow(inode, ext);

	return bh;
}

static struct buffer_head *
affs_get_extblock_slow(struct inode *inode, u32 ext)
{
	struct super_block *sb = inode->i_sb;
	struct buffer_head *bh;
	u32 ext_key;
	u32 lc_idx, lc_off, ac_idx;
	u32 tmp, idx;

	if (ext == AFFS_INODE->i_ext_last + 1) {
		/* read the next extended block from the current one */
		bh = AFFS_INODE->i_ext_bh;
		ext_key = be32_to_cpu(AFFS_TAIL(sb, bh)->extension);
		if (ext < AFFS_INODE->i_extcnt)
			goto read_ext;
		if (ext > AFFS_INODE->i_extcnt)
			BUG();
		bh = affs_alloc_extblock(inode, bh, ext);
		if (IS_ERR(bh))
			return bh;
		goto store_ext;
	}

	if (ext == 0) {
		/* we seek back to the file header block */
		ext_key = inode->i_ino;
		goto read_ext;
	}

	if (ext >= AFFS_INODE->i_extcnt) {
		struct buffer_head *prev_bh;

		/* allocate a new extended block */
		if (ext > AFFS_INODE->i_extcnt)
			BUG();

		/* get previous extended block */
		prev_bh = affs_get_extblock(inode, ext - 1);
		if (IS_ERR(prev_bh))
			return prev_bh;
		bh = affs_alloc_extblock(inode, prev_bh, ext);
		affs_brelse(prev_bh);
		if (IS_ERR(bh))
			return bh;
		goto store_ext;
	}

again:
	/* check if there is an extended cache and whether it's large enough */
	lc_idx = ext >> AFFS_INODE->i_lc_shift;
	lc_off = ext & AFFS_INODE->i_lc_mask;

	if (lc_idx >= AFFS_INODE->i_lc_size) {
		int err;

		err = affs_grow_extcache(inode, lc_idx);
		if (err)
			return ERR_PTR(err);
		goto again;
	}

	/* every n'th key we find in the linear cache */
	if (!lc_off) {
		ext_key = AFFS_INODE->i_lc[lc_idx];
		goto read_ext;
	}

	/* maybe it's still in the associative cache */
	ac_idx = (ext - lc_idx - 1) & AFFS_AC_MASK;
	if (AFFS_INODE->i_ac[ac_idx].ext == ext) {
		ext_key = AFFS_INODE->i_ac[ac_idx].key;
		goto read_ext;
	}

	/* try to find one of the previous extended blocks */
	tmp = ext;
	idx = ac_idx;
	while (--tmp, --lc_off > 0) {
		idx = (idx - 1) & AFFS_AC_MASK;
		if (AFFS_INODE->i_ac[idx].ext == tmp) {
			ext_key = AFFS_INODE->i_ac[idx].key;
			goto find_ext;
		}
	}

	/* fall back to the linear cache */
	ext_key = AFFS_INODE->i_lc[lc_idx];
find_ext:
	/* read all extended blocks until we find the one we need */
	//unlock cache
	do {
		bh = affs_bread(sb, ext_key);
		if (!bh)
			goto err_bread;
		ext_key = be32_to_cpu(AFFS_TAIL(sb, bh)->extension);
		affs_brelse(bh);
		tmp++;
	} while (tmp < ext);
	//lock cache

	/* store it in the associative cache */
	// recalculate ac_idx?
	AFFS_INODE->i_ac[ac_idx].ext = ext;
	AFFS_INODE->i_ac[ac_idx].key = ext_key;

read_ext:
	/* finally read the right extended block */
	//unlock cache
	bh = affs_bread(sb, ext_key);
	if (!bh)
		goto err_bread;
	//lock cache

store_ext:
	/* release old cached extended block and store the new one */
	affs_brelse(AFFS_INODE->i_ext_bh);
	AFFS_INODE->i_ext_last = ext;
	AFFS_INODE->i_ext_bh = bh;
	atomic_inc(&bh->b_count);

	return bh;

err_bread:
	affs_brelse(bh);
	return ERR_PTR(-EIO);
}

static int
affs_get_block(struct inode *inode, long block, struct buffer_head *bh_result, int create)
{
	struct super_block	*sb = inode->i_sb;
	struct buffer_head	*ext_bh;
	u32			 ext;

	pr_debug("AFFS: get_block(%u, %ld)\n", (u32)inode->i_ino, block);

	if (block < 0)
		goto err_small;

	if (block >= AFFS_INODE->i_blkcnt) {
		if (block > AFFS_INODE->i_blkcnt || !create)
			goto err_big;
	} else
		create = 0;

	//lock cache
	affs_lock_ext(inode);

	ext = block / AFFS_SB->s_hashsize;
	block -= ext * AFFS_SB->s_hashsize;
	ext_bh = affs_get_extblock(inode, ext);
	if (IS_ERR(ext_bh))
		goto err_ext;
	bh_result->b_blocknr = be32_to_cpu(AFFS_BLOCK(sb, ext_bh, block));
	bh_result->b_dev = inode->i_dev;
	bh_result->b_state |= (1UL << BH_Mapped);

	if (create) {
		u32 blocknr = affs_alloc_block(inode, ext_bh->b_blocknr);
		if (!blocknr)
			goto err_alloc;
		bh_result->b_state |= (1UL << BH_New);
		AFFS_INODE->mmu_private += AFFS_SB->s_data_blksize;
		AFFS_INODE->i_blkcnt++;

		/* store new block */
		if (bh_result->b_blocknr)
			affs_warning(sb, "get_block", "block already set (%x)", bh_result->b_blocknr);
		AFFS_BLOCK(sb, ext_bh, block) = cpu_to_be32(blocknr);
		AFFS_HEAD(ext_bh)->block_count = cpu_to_be32(block + 1);
		affs_adjust_checksum(ext_bh, blocknr - bh_result->b_blocknr + 1);
		bh_result->b_blocknr = blocknr;

		if (!block) {
			/* insert first block into header block */
			u32 tmp = be32_to_cpu(AFFS_HEAD(ext_bh)->first_data);
			if (tmp)
				affs_warning(sb, "get_block", "first block already set (%d)", tmp);
			AFFS_HEAD(ext_bh)->first_data = cpu_to_be32(blocknr);
			affs_adjust_checksum(ext_bh, blocknr - tmp);
		}
	}

	affs_brelse(ext_bh);
	//unlock cache
	affs_unlock_ext(inode);
	return 0;

err_small:
	affs_error(inode->i_sb,"get_block","Block < 0");
	return -EIO;
err_big:
	affs_error(inode->i_sb,"get_block","strange block request %d", block);
	return -EIO;
err_ext:
	// unlock cache
	affs_unlock_ext(inode);
	return PTR_ERR(ext_bh);
err_alloc:
	brelse(ext_bh);
	bh_result->b_state &= ~(1UL << BH_Mapped);
	// unlock cache
	affs_unlock_ext(inode);
	return -ENOSPC;
}

static int affs_writepage(struct page *page)
{
	return block_write_full_page(page, affs_get_block);
}
static int affs_readpage(struct file *file, struct page *page)
{
	return block_read_full_page(page, affs_get_block);
}
static int affs_prepare_write(struct file *file, struct page *page, unsigned from, unsigned to)
{
	return cont_prepare_write(page, from, to, affs_get_block,
		&page->mapping->host->u.affs_i.mmu_private);
}
static int _affs_bmap(struct address_space *mapping, long block)
{
	return generic_block_bmap(mapping,block,affs_get_block);
}
struct address_space_operations affs_aops = {
	readpage: affs_readpage,
	writepage: affs_writepage,
	sync_page: block_sync_page,
	prepare_write: affs_prepare_write,
	commit_write: generic_commit_write,
	bmap: _affs_bmap
};

static inline struct buffer_head *
affs_bread_ino(struct inode *inode, int block, int create)
{
	struct buffer_head *bh, tmp_bh;
	int err;

	tmp_bh.b_state = 0;
	err = affs_get_block(inode, block, &tmp_bh, create);
	if (!err) {
		bh = affs_bread(inode->i_sb, tmp_bh.b_blocknr);
		if (bh) {
			bh->b_state |= tmp_bh.b_state;
			return bh;
		}
		err = -EIO;
	}
	return ERR_PTR(err);
}

static inline struct buffer_head *
affs_getzeroblk_ino(struct inode *inode, int block)
{
	struct buffer_head *bh, tmp_bh;
	int err;

	tmp_bh.b_state = 0;
	err = affs_get_block(inode, block, &tmp_bh, 1);
	if (!err) {
		bh = affs_getzeroblk(inode->i_sb, tmp_bh.b_blocknr);