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Revision 7fb5409df092589b86cc9412d926879cb572b7f0 authored by Jan Kara on 10 February 2008, 06:08:38 UTC, committed by Theodore Ts'o on 10 February 2008, 06:08:38 UTC 
ext4: Fix Direct I/O locking
 
We cannot start transaction in ext4_direct_IO() and just let it last
during the whole write because dio_get_page() acquires mmap_sem which
ranks above transaction start (e.g. because we have dependency chain
mmap_sem->PageLock->journal_start, or because we update atime while
holding mmap_sem) and thus deadlocks could happen. We solve the problem
by starting a transaction separately for each ext4_get_block() call.

We *could* have a problem that we allocate a block and before its data
are written out the machine crashes and thus we expose stale data. But
that does not happen because for hole-filling generic code falls back to
buffered writes and for file extension, we add inode to orphan list and
thus in case of crash, journal replay will truncate inode back to the
original size.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Mingming Cao <cmm@us.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
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Raw File
hash.c 
/*
 * Cryptographic Hash operations.
 * 
 * Copyright (c) 2006 Herbert Xu <herbert@gondor.apana.org.au>
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the Free
 * Software Foundation; either version 2 of the License, or (at your option) 
 * any later version.
 */

#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/seq_file.h>

#include "internal.h"

static unsigned int crypto_hash_ctxsize(struct crypto_alg *alg, u32 type,
					u32 mask)
{
	return alg->cra_ctxsize;
}

static int hash_setkey_unaligned(struct crypto_hash *crt, const u8 *key,
		                 unsigned int keylen)
{
	struct crypto_tfm *tfm = crypto_hash_tfm(crt);
	struct hash_alg *alg = &tfm->__crt_alg->cra_hash;
	unsigned long alignmask = crypto_hash_alignmask(crt);
	int ret;
	u8 *buffer, *alignbuffer;
	unsigned long absize;

	absize = keylen + alignmask;
	buffer = kmalloc(absize, GFP_ATOMIC);
	if (!buffer)
		return -ENOMEM;

	alignbuffer = (u8 *)ALIGN((unsigned long)buffer, alignmask + 1);
	memcpy(alignbuffer, key, keylen);
	ret = alg->setkey(crt, alignbuffer, keylen);
	memset(alignbuffer, 0, keylen);
	kfree(buffer);
	return ret;
}

static int hash_setkey(struct crypto_hash *crt, const u8 *key,
		       unsigned int keylen)
{
	struct crypto_tfm *tfm = crypto_hash_tfm(crt);
	struct hash_alg *alg = &tfm->__crt_alg->cra_hash;
	unsigned long alignmask = crypto_hash_alignmask(crt);

	if ((unsigned long)key & alignmask)
		return hash_setkey_unaligned(crt, key, keylen);

	return alg->setkey(crt, key, keylen);
}

static int crypto_init_hash_ops(struct crypto_tfm *tfm, u32 type, u32 mask)
{
	struct hash_tfm *crt = &tfm->crt_hash;
	struct hash_alg *alg = &tfm->__crt_alg->cra_hash;

	if (alg->digestsize > crypto_tfm_alg_blocksize(tfm))
		return -EINVAL;

	crt->init = alg->init;
	crt->update = alg->update;
	crt->final = alg->final;
	crt->digest = alg->digest;
	crt->setkey = hash_setkey;
	crt->digestsize = alg->digestsize;

	return 0;
}

static void crypto_hash_show(struct seq_file *m, struct crypto_alg *alg)
	__attribute__ ((unused));
static void crypto_hash_show(struct seq_file *m, struct crypto_alg *alg)
{
	seq_printf(m, "type         : hash\n");
	seq_printf(m, "blocksize    : %u\n", alg->cra_blocksize);
	seq_printf(m, "digestsize   : %u\n", alg->cra_hash.digestsize);
}

const struct crypto_type crypto_hash_type = {
	.ctxsize = crypto_hash_ctxsize,
	.init = crypto_init_hash_ops,
#ifdef CONFIG_PROC_FS
	.show = crypto_hash_show,
#endif
};
EXPORT_SYMBOL_GPL(crypto_hash_type);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Generic cryptographic hash type");
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