/* vi: set sw=4 ts=4: */
/*
 * unix_io.c --- This is the Unix (well, really POSIX) implementation
 *      of the I/O manager.
 *
 * Implements a one-block write-through cache.
 *
 * Includes support for Windows NT support under Cygwin.
 *
 * Copyright (C) 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001,
 *      2002 by Theodore Ts'o.
 *
 * %Begin-Header%
 * This file may be redistributed under the terms of the GNU Public
 * License.
 * %End-Header%
 */

#include <stdio.h>
#include <string.h>
#if HAVE_UNISTD_H
#include <unistd.h>
#endif
#if HAVE_ERRNO_H
#include <errno.h>
#endif
#include <fcntl.h>
#include <time.h>
#ifdef __linux__
#include <sys/utsname.h>
#endif
#if HAVE_SYS_STAT_H
#include <sys/stat.h>
#endif
#if HAVE_SYS_TYPES_H
#include <sys/types.h>
#endif
#include <sys/resource.h>

#include "ext2_fs.h"
#include "ext2fs.h"

/*
 * For checking structure magic numbers...
 */

#define EXT2_CHECK_MAGIC(struct, code) \
          if ((struct)->magic != (code)) return (code)

struct unix_cache {
        char            *buf;
        unsigned long   block;
        int             access_time;
        unsigned        dirty:1;
        unsigned        in_use:1;
};

#define CACHE_SIZE 8
#define WRITE_DIRECT_SIZE 4     /* Must be smaller than CACHE_SIZE */
#define READ_DIRECT_SIZE 4      /* Should be smaller than CACHE_SIZE */

struct unix_private_data {
        int     magic;
        int     dev;
        int     flags;
        int     access_time;
        ext2_loff_t offset;
        struct unix_cache cache[CACHE_SIZE];
};

static errcode_t unix_open(const char *name, int flags, io_channel *channel);
static errcode_t unix_close(io_channel channel);
static errcode_t unix_set_blksize(io_channel channel, int blksize);
static errcode_t unix_read_blk(io_channel channel, unsigned long block,
                               int count, void *data);
static errcode_t unix_write_blk(io_channel channel, unsigned long block,
                                int count, const void *data);
static errcode_t unix_flush(io_channel channel);
static errcode_t unix_write_byte(io_channel channel, unsigned long offset,
                                int size, const void *data);
static errcode_t unix_set_option(io_channel channel, const char *option,
                                 const char *arg);

static void reuse_cache(io_channel channel, struct unix_private_data *data,
                 struct unix_cache *cache, unsigned long block);

/* __FreeBSD_kernel__ is defined by GNU/kFreeBSD - the FreeBSD kernel
 * does not know buffered block devices - everything is raw. */
#if defined(__CYGWIN__) || defined(__FreeBSD__) || defined(__FreeBSD_kernel__)
#define NEED_BOUNCE_BUFFER
#else
#undef NEED_BOUNCE_BUFFER
#endif

static struct struct_io_manager struct_unix_manager = {
        EXT2_ET_MAGIC_IO_MANAGER,
        "Unix I/O Manager",
        unix_open,
        unix_close,
        unix_set_blksize,
        unix_read_blk,
        unix_write_blk,
        unix_flush,
#ifdef NEED_BOUNCE_BUFFER
        0,
#else
        unix_write_byte,
#endif
        unix_set_option
};

io_manager unix_io_manager = &struct_unix_manager;

/*
 * Here are the raw I/O functions
 */
#ifndef NEED_BOUNCE_BUFFER
static errcode_t raw_read_blk(io_channel channel,
                              struct unix_private_data *data,
                              unsigned long block,
                              int count, void *buf)
{
        errcode_t       retval;
        ssize_t         size;
        ext2_loff_t     location;
        int             actual = 0;

        size = (count < 0) ? -count : count * channel->block_size;
        location = ((ext2_loff_t) block * channel->block_size) + data->offset;
        if (ext2fs_llseek(data->dev, location, SEEK_SET) != location) {
                retval = errno ? errno : EXT2_ET_LLSEEK_FAILED;
                goto error_out;
        }
        actual = read(data->dev, buf, size);
        if (actual != size) {
                if (actual < 0)
                        actual = 0;
                retval = EXT2_ET_SHORT_READ;
                goto error_out;
        }
        return 0;

error_out:
        memset((char *) buf+actual, 0, size-actual);
        if (channel->read_error)
                retval = (channel->read_error)(channel, block, count, buf,
                                               size, actual, retval);
        return retval;
}
#else /* NEED_BOUNCE_BUFFER */
/*
 * Windows and FreeBSD block devices only allow sector alignment IO in offset and size
 */
static errcode_t raw_read_blk(io_channel channel,
                              struct unix_private_data *data,
                              unsigned long block,
                              int count, void *buf)
{
        errcode_t       retval;
        size_t          size, alignsize, fragment;
        ext2_loff_t     location;
        int             total = 0, actual;
#define BLOCKALIGN 512
        char            sector[BLOCKALIGN];

        size = (count < 0) ? -count : count * channel->block_size;
        location = ((ext2_loff_t) block * channel->block_size) + data->offset;
#ifdef DEBUG
        printf("count=%d, size=%d, block=%d, blk_size=%d, location=%lx\n",
                        count, size, block, channel->block_size, location);
#endif
        if (ext2fs_llseek(data->dev, location, SEEK_SET) != location) {
                retval = errno ? errno : EXT2_ET_LLSEEK_FAILED;
                goto error_out;
        }
        fragment = size % BLOCKALIGN;
        alignsize = size - fragment;
        if (alignsize) {
                actual = read(data->dev, buf, alignsize);
                if (actual != alignsize)
                        goto short_read;
        }
        if (fragment) {
                actual = read(data->dev, sector, BLOCKALIGN);
                if (actual != BLOCKALIGN)
                        goto short_read;
                memcpy(buf+alignsize, sector, fragment);
        }
        return 0;

short_read:
        if (actual>0)
                total += actual;
        retval = EXT2_ET_SHORT_READ;

error_out:
        memset((char *) buf+total, 0, size-actual);
        if (channel->read_error)
                retval = (channel->read_error)(channel, block, count, buf,
                                               size, actual, retval);
        return retval;
}
#endif

static errcode_t raw_write_blk(io_channel channel,
                               struct unix_private_data *data,
                               unsigned long block,
                               int count, const void *buf)
{
        ssize_t         size;
        ext2_loff_t     location;
        int             actual = 0;
        errcode_t       retval;

        if (count == 1)
                size = channel->block_size;
        else {
                if (count < 0)
                        size = -count;
                else
                        size = count * channel->block_size;
        }

        location = ((ext2_loff_t) block * channel->block_size) + data->offset;
        if (ext2fs_llseek(data->dev, location, SEEK_SET) != location) {
                retval = errno ? errno : EXT2_ET_LLSEEK_FAILED;
                goto error_out;
        }

        actual = write(data->dev, buf, size);
        if (actual != size) {
                retval = EXT2_ET_SHORT_WRITE;
                goto error_out;
        }
        return 0;

error_out:
        if (channel->write_error)
                retval = (channel->write_error)(channel, block, count, buf,
                                                size, actual, retval);
        return retval;
}


/*
 * Here we implement the cache functions
 */

/* Allocate the cache buffers */
static errcode_t alloc_cache(io_channel channel,
                             struct unix_private_data *data)
{
        errcode_t               retval;
        struct unix_cache       *cache;
        int                     i;

        data->access_time = 0;
        for (i=0, cache = data->cache; i < CACHE_SIZE; i++, cache++) {
                cache->block = 0;
                cache->access_time = 0;
                cache->dirty = 0;
                cache->in_use = 0;
                if ((retval = ext2fs_get_mem(channel->block_size,
                                             &cache->buf)))
                        return retval;
        }
        return 0;
}

/* Free the cache buffers */
static void free_cache(struct unix_private_data *data)
{
        struct unix_cache       *cache;
        int                     i;

        data->access_time = 0;
        for (i=0, cache = data->cache; i < CACHE_SIZE; i++, cache++) {
                cache->block = 0;
                cache->access_time = 0;
                cache->dirty = 0;
                cache->in_use = 0;
                ext2fs_free_mem(&cache->buf);
                cache->buf = 0;
        }
}

#ifndef NO_IO_CACHE
/*
 * Try to find a block in the cache.  If the block is not found, and
 * eldest is a non-zero pointer, then fill in eldest with the cache
 * entry to that should be reused.
 */
static struct unix_cache *find_cached_block(struct unix_private_data *data,
                                            unsigned long block,
                                            struct unix_cache **eldest)
{
        struct unix_cache       *cache, *unused_cache, *oldest_cache;
        int                     i;

        unused_cache = oldest_cache = 0;
        for (i=0, cache = data->cache; i < CACHE_SIZE; i++, cache++) {
                if (!cache->in_use) {
                        if (!unused_cache)
                                unused_cache = cache;
                        continue;
                }
                if (cache->block == block) {
                        cache->access_time = ++data->access_time;
                        return cache;
                }
                if (!oldest_cache ||
                    (cache->access_time < oldest_cache->access_time))
                        oldest_cache = cache;
        }
        if (eldest)
                *eldest = (unused_cache) ? unused_cache : oldest_cache;
        return 0;
}

/*
 * Reuse a particular cache entry for another block.
 */
static void reuse_cache(io_channel channel, struct unix_private_data *data,
                 struct unix_cache *cache, unsigned long block)
{
        if (cache->dirty && cache->in_use)
                raw_write_blk(channel, data, cache->block, 1, cache->buf);

        cache->in_use = 1;
        cache->dirty = 0;
        cache->block = block;
        cache->access_time = ++data->access_time;
}

/*
 * Flush all of the blocks in the cache
 */
static errcode_t flush_cached_blocks(io_channel channel,
                                     struct unix_private_data *data,
                                     int invalidate)

{
        struct unix_cache       *cache;
        errcode_t               retval, retval2;
        int                     i;

        retval2 = 0;
        for (i=0, cache = data->cache; i < CACHE_SIZE; i++, cache++) {
                if (!cache->in_use)
                        continue;

                if (invalidate)
                        cache->in_use = 0;

                if (!cache->dirty)
                        continue;

                retval = raw_write_blk(channel, data,
                                       cache->block, 1, cache->buf);
                if (retval)
                        retval2 = retval;
                else
                        cache->dirty = 0;
        }
        return retval2;
}
#endif /* NO_IO_CACHE */

static errcode_t unix_open(const char *name, int flags, io_channel *channel)
{
        io_channel      io = NULL;
        struct unix_private_data *data = NULL;
        errcode_t       retval;
        int             open_flags;
        struct stat     st;
#ifdef __linux__
        struct          utsname ut;
#endif

        if (name == 0)
                return EXT2_ET_BAD_DEVICE_NAME;
        retval = ext2fs_get_mem(sizeof(struct struct_io_channel), &io);
        if (retval)
                return retval;
        memset(io, 0, sizeof(struct struct_io_channel));
        io->magic = EXT2_ET_MAGIC_IO_CHANNEL;
        retval = ext2fs_get_mem(sizeof(struct unix_private_data), &data);
        if (retval)
                goto cleanup;

        io->manager = unix_io_manager;
        retval = ext2fs_get_mem(strlen(name)+1, &io->name);
        if (retval)
                goto cleanup;

        strcpy(io->name, name);
        io->private_data = data;
        io->block_size = 1024;
        io->read_error = 0;
        io->write_error = 0;
        io->refcount = 1;

        memset(data, 0, sizeof(struct unix_private_data));
        data->magic = EXT2_ET_MAGIC_UNIX_IO_CHANNEL;

        if ((retval = alloc_cache(io, data)))
                goto cleanup;

        open_flags = (flags & IO_FLAG_RW) ? O_RDWR : O_RDONLY;
#ifdef CONFIG_LFS
        data->dev = open64(io->name, open_flags);
#else
        data->dev = open(io->name, open_flags);
#endif
        if (data->dev < 0) {
                retval = errno;
                goto cleanup;
        }

#ifdef __linux__
#undef RLIM_INFINITY
#if (defined(__alpha__) || ((defined(__sparc__) || defined(__mips__)) && (SIZEOF_LONG == 4)))
#define RLIM_INFINITY   ((unsigned long)(~0UL>>1))
#else
#define RLIM_INFINITY  (~0UL)
#endif
        /*
         * Work around a bug in 2.4.10-2.4.18 kernels where writes to
         * block devices are wrongly getting hit by the filesize
         * limit.  This workaround isn't perfect, since it won't work
         * if glibc wasn't built against 2.2 header files.  (Sigh.)
         *
         */
        if ((flags & IO_FLAG_RW) &&
            (uname(&ut) == 0) &&
            ((ut.release[0] == '2') && (ut.release[1] == '.') &&
             (ut.release[2] == '4') && (ut.release[3] == '.') &&
             (ut.release[4] == '1') && (ut.release[5] >= '0') &&
             (ut.release[5] < '8')) &&
            (fstat(data->dev, &st) == 0) &&
            (S_ISBLK(st.st_mode))) {
                struct rlimit   rlim;

                rlim.rlim_cur = rlim.rlim_max = (unsigned long) RLIM_INFINITY;
                setrlimit(RLIMIT_FSIZE, &rlim);
                getrlimit(RLIMIT_FSIZE, &rlim);
                if (((unsigned long) rlim.rlim_cur) <
                    ((unsigned long) rlim.rlim_max)) {
                        rlim.rlim_cur = rlim.rlim_max;
                        setrlimit(RLIMIT_FSIZE, &rlim);
                }
        }
#endif
        *channel = io;
        return 0;

cleanup:
        if (data) {
                free_cache(data);
                ext2fs_free_mem(&data);
        }
        ext2fs_free_mem(&io);
        return retval;
}

static errcode_t unix_close(io_channel channel)
{
        struct unix_private_data *data;
        errcode_t       retval = 0;

        EXT2_CHECK_MAGIC(channel, EXT2_ET_MAGIC_IO_CHANNEL);
        data = (struct unix_private_data *) channel->private_data;
        EXT2_CHECK_MAGIC(data, EXT2_ET_MAGIC_UNIX_IO_CHANNEL);

        if (--channel->refcount > 0)
                return 0;

#ifndef NO_IO_CACHE
        retval = flush_cached_blocks(channel, data, 0);
#endif

        if (close(data->dev) < 0)
                retval = errno;
        free_cache(data);

        ext2fs_free_mem(&channel->private_data);
        ext2fs_free_mem(&channel->name);
        ext2fs_free_mem(&channel);
        return retval;
}

static errcode_t unix_set_blksize(io_channel channel, int blksize)
{
        struct unix_private_data *data;
        errcode_t               retval;

        EXT2_CHECK_MAGIC(channel, EXT2_ET_MAGIC_IO_CHANNEL);
        data = (struct unix_private_data *) channel->private_data;
        EXT2_CHECK_MAGIC(data, EXT2_ET_MAGIC_UNIX_IO_CHANNEL);

        if (channel->block_size != blksize) {
#ifndef NO_IO_CACHE
                if ((retval = flush_cached_blocks(channel, data, 0)))
                        return retval;
#endif

                channel->block_size = blksize;
                free_cache(data);
                if ((retval = alloc_cache(channel, data)))
                        return retval;
        }
        return 0;
}


static errcode_t unix_read_blk(io_channel channel, unsigned long block,
                               int count, void *buf)
{
        struct unix_private_data *data;
        struct unix_cache *cache, *reuse[READ_DIRECT_SIZE];
        errcode_t       retval;
        char            *cp;
        int             i, j;

        EXT2_CHECK_MAGIC(channel, EXT2_ET_MAGIC_IO_CHANNEL);
        data = (struct unix_private_data *) channel->private_data;
        EXT2_CHECK_MAGIC(data, EXT2_ET_MAGIC_UNIX_IO_CHANNEL);

#ifdef NO_IO_CACHE
        return raw_read_blk(channel, data, block, count, buf);
#else
        /*
         * If we're doing an odd-sized read or a very large read,
         * flush out the cache and then do a direct read.
         */
        if (count < 0 || count > WRITE_DIRECT_SIZE) {
                if ((retval = flush_cached_blocks(channel, data, 0)))
                        return retval;
                return raw_read_blk(channel, data, block, count, buf);
        }

        cp = buf;
        while (count > 0) {
                /* If it's in the cache, use it! */
                if ((cache = find_cached_block(data, block, &reuse[0]))) {
#ifdef DEBUG
                        printf("Using cached block %d\n", block);
#endif
                        memcpy(cp, cache->buf, channel->block_size);
                        count--;
                        block++;
                        cp += channel->block_size;
                        continue;
                }
                /*
                 * Find the number of uncached blocks so we can do a
                 * single read request
                 */
                for (i=1; i < count; i++)
                        if (find_cached_block(data, block+i, &reuse[i]))
                                break;
#ifdef DEBUG
                printf("Reading %d blocks starting at %d\n", i, block);
#endif
                if ((retval = raw_read_blk(channel, data, block, i, cp)))
                        return retval;

                /* Save the results in the cache */
                for (j=0; j < i; j++) {
                        count--;
                        cache = reuse[j];
                        reuse_cache(channel, data, cache, block++);
                        memcpy(cache->buf, cp, channel->block_size);
                        cp += channel->block_size;
                }
        }
        return 0;
#endif /* NO_IO_CACHE */
}

static errcode_t unix_write_blk(io_channel channel, unsigned long block,
                                int count, const void *buf)
{
        struct unix_private_data *data;
        struct unix_cache *cache, *reuse;
        errcode_t       retval = 0;
        const char      *cp;
        int             writethrough;

        EXT2_CHECK_MAGIC(channel, EXT2_ET_MAGIC_IO_CHANNEL);
        data = (struct unix_private_data *) channel->private_data;
        EXT2_CHECK_MAGIC(data, EXT2_ET_MAGIC_UNIX_IO_CHANNEL);

#ifdef NO_IO_CACHE
        return raw_write_blk(channel, data, block, count, buf);
#else
        /*
         * If we're doing an odd-sized write or a very large write,
         * flush out the cache completely and then do a direct write.
         */
        if (count < 0 || count > WRITE_DIRECT_SIZE) {
                if ((retval = flush_cached_blocks(channel, data, 1)))
                        return retval;
                return raw_write_blk(channel, data, block, count, buf);
        }

        /*
         * For a moderate-sized multi-block write, first force a write
         * if we're in write-through cache mode, and then fill the
         * cache with the blocks.
         */
        writethrough = channel->flags & CHANNEL_FLAGS_WRITETHROUGH;
        if (writethrough)
                retval = raw_write_blk(channel, data, block, count, buf);

        cp = buf;
        while (count > 0) {
                cache = find_cached_block(data, block, &reuse);
                if (!cache) {
                        cache = reuse;
                        reuse_cache(channel, data, cache, block);
                }
                memcpy(cache->buf, cp, channel->block_size);
                cache->dirty = !writethrough;
                count--;
                block++;
                cp += channel->block_size;
        }
        return retval;
#endif /* NO_IO_CACHE */
}

static errcode_t unix_write_byte(io_channel channel, unsigned long offset,
                                 int size, const void *buf)
{
        struct unix_private_data *data;
        errcode_t       retval = 0;
        ssize_t         actual;

        EXT2_CHECK_MAGIC(channel, EXT2_ET_MAGIC_IO_CHANNEL);
        data = (struct unix_private_data *) channel->private_data;
        EXT2_CHECK_MAGIC(data, EXT2_ET_MAGIC_UNIX_IO_CHANNEL);

#ifndef NO_IO_CACHE
        /*
         * Flush out the cache completely
         */
        if ((retval = flush_cached_blocks(channel, data, 1)))
                return retval;
#endif

        if (lseek(data->dev, offset + data->offset, SEEK_SET) < 0)
                return errno;

        actual = write(data->dev, buf, size);
        if (actual != size)
                return EXT2_ET_SHORT_WRITE;

        return 0;
}

/*
 * Flush data buffers to disk.
 */
static errcode_t unix_flush(io_channel channel)
{
        struct unix_private_data *data;
        errcode_t retval = 0;

        EXT2_CHECK_MAGIC(channel, EXT2_ET_MAGIC_IO_CHANNEL);
        data = (struct unix_private_data *) channel->private_data;
        EXT2_CHECK_MAGIC(data, EXT2_ET_MAGIC_UNIX_IO_CHANNEL);

#ifndef NO_IO_CACHE
        retval = flush_cached_blocks(channel, data, 0);
#endif
        fsync(data->dev);
        return retval;
}

static errcode_t unix_set_option(io_channel channel, const char *option,
                                 const char *arg)
{
        struct unix_private_data *data;
        unsigned long tmp;
        char *end;

        EXT2_CHECK_MAGIC(channel, EXT2_ET_MAGIC_IO_CHANNEL);
        data = (struct unix_private_data *) channel->private_data;
        EXT2_CHECK_MAGIC(data, EXT2_ET_MAGIC_UNIX_IO_CHANNEL);

        if (!strcmp(option, "offset")) {
                if (!arg)
                        return EXT2_ET_INVALID_ARGUMENT;

                tmp = strtoul(arg, &end, 0);
                if (*end)
                        return EXT2_ET_INVALID_ARGUMENT;
                data->offset = tmp;
                return 0;
        }
        return EXT2_ET_INVALID_ARGUMENT;
}