/* -*- mode: c; c-basic-offset: 8; -*-
 * vim: noexpandtab sw=8 ts=8 sts=0:
 *
 * io.c
 *
 * Buffer cache handling
 *
 * Copyright (C) 2002, 2004 Oracle.  All rights reserved.
 *
 * 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.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public
 * License along with this program; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 021110-1307, USA.
 */

#include <linux/fs.h>
#include <linux/types.h>
#include <linux/slab.h>
#include <linux/highmem.h>

#include <cluster/masklog.h>

#include "ocfs2.h"

#include "alloc.h"
#include "inode.h"
#include "journal.h"
#include "uptodate.h"

#include "buffer_head_io.h"

int ocfs2_write_block(struct ocfs2_super *osb, struct buffer_head *bh,
                      struct inode *inode)
{
        int ret = 0;

        mlog_entry("(bh->b_blocknr = %llu, inode=%p)\n",
                   (unsigned long long)bh->b_blocknr, inode);

        BUG_ON(bh->b_blocknr < OCFS2_SUPER_BLOCK_BLKNO);
        BUG_ON(buffer_jbd(bh));

        /* No need to check for a soft readonly file system here. non
         * journalled writes are only ever done on system files which
         * can get modified during recovery even if read-only. */
        if (ocfs2_is_hard_readonly(osb)) {
                ret = -EROFS;
                goto out;
        }

        mutex_lock(&OCFS2_I(inode)->ip_io_mutex);

        lock_buffer(bh);
        set_buffer_uptodate(bh);

        /* remove from dirty list before I/O. */
        clear_buffer_dirty(bh);

        get_bh(bh); /* for end_buffer_write_sync() */                   
        bh->b_end_io = end_buffer_write_sync;
        submit_bh(WRITE, bh);

        wait_on_buffer(bh);

        if (buffer_uptodate(bh)) {
                ocfs2_set_buffer_uptodate(inode, bh);
        } else {
                /* We don't need to remove the clustered uptodate
                 * information for this bh as it's not marked locally
                 * uptodate. */
                ret = -EIO;
                put_bh(bh);
        }

        mutex_unlock(&OCFS2_I(inode)->ip_io_mutex);
out:
        mlog_exit(ret);
        return ret;
}

int ocfs2_read_blocks(struct ocfs2_super *osb, u64 block, int nr,
                      struct buffer_head *bhs[], int flags,
                      struct inode *inode)
{
        int status = 0;
        struct super_block *sb;
        int i, ignore_cache = 0;
        struct buffer_head *bh;

        mlog_entry("(block=(%llu), nr=(%d), flags=%d, inode=%p)\n",
                   (unsigned long long)block, nr, flags, inode);

        BUG_ON((flags & OCFS2_BH_READAHEAD) &&
               (!inode || !(flags & OCFS2_BH_CACHED)));

        if (osb == NULL || osb->sb == NULL || bhs == NULL) {
                status = -EINVAL;
                mlog_errno(status);
                goto bail;
        }

        if (nr < 0) {
                mlog(ML_ERROR, "asked to read %d blocks!\n", nr);
                status = -EINVAL;
                mlog_errno(status);
                goto bail;
        }

        if (nr == 0) {
                mlog(ML_BH_IO, "No buffers will be read!\n");
                status = 0;
                goto bail;
        }

        sb = osb->sb;

        if (flags & OCFS2_BH_CACHED && !inode)
                flags &= ~OCFS2_BH_CACHED;

        if (inode)
                mutex_lock(&OCFS2_I(inode)->ip_io_mutex);
        for (i = 0 ; i < nr ; i++) {
                if (bhs[i] == NULL) {
                        bhs[i] = sb_getblk(sb, block++);
                        if (bhs[i] == NULL) {
                                if (inode)
                                        mutex_unlock(&OCFS2_I(inode)->ip_io_mutex);
                                status = -EIO;
                                mlog_errno(status);
                                goto bail;
                        }
                }
                bh = bhs[i];
                ignore_cache = 0;

                /* There are three read-ahead cases here which we need to
                 * be concerned with. All three assume a buffer has
                 * previously been submitted with OCFS2_BH_READAHEAD
                 * and it hasn't yet completed I/O.
                 *
                 * 1) The current request is sync to disk. This rarely
                 *    happens these days, and never when performance
                 *    matters - the code can just wait on the buffer
                 *    lock and re-submit.
                 *
                 * 2) The current request is cached, but not
                 *    readahead. ocfs2_buffer_uptodate() will return
                 *    false anyway, so we'll wind up waiting on the
                 *    buffer lock to do I/O. We re-check the request
                 *    with after getting the lock to avoid a re-submit.
                 *
                 * 3) The current request is readahead (and so must
                 *    also be a caching one). We short circuit if the
                 *    buffer is locked (under I/O) and if it's in the
                 *    uptodate cache. The re-check from #2 catches the
                 *    case that the previous read-ahead completes just
                 *    before our is-it-in-flight check.
                 */

                if (flags & OCFS2_BH_CACHED &&
                    !ocfs2_buffer_uptodate(inode, bh)) {
                        mlog(ML_UPTODATE,
                             "bh (%llu), inode %llu not uptodate\n",
                             (unsigned long long)bh->b_blocknr,
                             (unsigned long long)OCFS2_I(inode)->ip_blkno);
                        ignore_cache = 1;
                }

                /* XXX: Can we ever get this and *not* have the cached
                 * flag set? */
                if (buffer_jbd(bh)) {
                        if (!(flags & OCFS2_BH_CACHED) || ignore_cache)
                                mlog(ML_BH_IO, "trying to sync read a jbd "
                                               "managed bh (blocknr = %llu)\n",
                                     (unsigned long long)bh->b_blocknr);
                        continue;
                }

                if (!(flags & OCFS2_BH_CACHED) || ignore_cache) {
                        if (buffer_dirty(bh)) {
                                /* This should probably be a BUG, or
                                 * at least return an error. */
                                mlog(ML_BH_IO, "asking me to sync read a dirty "
                                               "buffer! (blocknr = %llu)\n",
                                     (unsigned long long)bh->b_blocknr);
                                continue;
                        }

                        /* A read-ahead request was made - if the
                         * buffer is already under read-ahead from a
                         * previously submitted request than we are
                         * done here. */
                        if ((flags & OCFS2_BH_READAHEAD)
                            && ocfs2_buffer_read_ahead(inode, bh))
                                continue;

                        lock_buffer(bh);
                        if (buffer_jbd(bh)) {
#ifdef CATCH_BH_JBD_RACES
                                mlog(ML_ERROR, "block %llu had the JBD bit set "
                                               "while I was in lock_buffer!",
                                     (unsigned long long)bh->b_blocknr);
                                BUG();
#else
                                unlock_buffer(bh);
                                continue;
#endif
                        }

                        /* Re-check ocfs2_buffer_uptodate() as a
                         * previously read-ahead buffer may have
                         * completed I/O while we were waiting for the
                         * buffer lock. */
                        if ((flags & OCFS2_BH_CACHED)
                            && !(flags & OCFS2_BH_READAHEAD)
                            && ocfs2_buffer_uptodate(inode, bh)) {
                                unlock_buffer(bh);
                                continue;
                        }

                        clear_buffer_uptodate(bh);
                        get_bh(bh); /* for end_buffer_read_sync() */
                        bh->b_end_io = end_buffer_read_sync;
                        submit_bh(READ, bh);
                        continue;
                }
        }

        status = 0;

        for (i = (nr - 1); i >= 0; i--) {
                bh = bhs[i];

                if (!(flags & OCFS2_BH_READAHEAD)) {
                        /* We know this can't have changed as we hold the
                         * inode sem. Avoid doing any work on the bh if the
                         * journal has it. */
                        if (!buffer_jbd(bh))
                                wait_on_buffer(bh);

                        if (!buffer_uptodate(bh)) {
                                /* Status won't be cleared from here on out,
                                 * so we can safely record this and loop back
                                 * to cleanup the other buffers. Don't need to
                                 * remove the clustered uptodate information
                                 * for this bh as it's not marked locally
                                 * uptodate. */
                                status = -EIO;
                                put_bh(bh);
                                bhs[i] = NULL;
                                continue;
                        }
                }

                /* Always set the buffer in the cache, even if it was
                 * a forced read, or read-ahead which hasn't yet
                 * completed. */
                if (inode)
                        ocfs2_set_buffer_uptodate(inode, bh);
        }
        if (inode)
                mutex_unlock(&OCFS2_I(inode)->ip_io_mutex);

        mlog(ML_BH_IO, "block=(%llu), nr=(%d), cached=%s, flags=0x%x\n", 
             (unsigned long long)block, nr,
             (!(flags & OCFS2_BH_CACHED) || ignore_cache) ? "no" : "yes", flags);

bail:

        mlog_exit(status);
        return status;
}

/* Check whether the blkno is the super block or one of the backups. */
static void ocfs2_check_super_or_backup(struct super_block *sb,
                                        sector_t blkno)
{
        int i;
        u64 backup_blkno;

        if (blkno == OCFS2_SUPER_BLOCK_BLKNO)
                return;

        for (i = 0; i < OCFS2_MAX_BACKUP_SUPERBLOCKS; i++) {
                backup_blkno = ocfs2_backup_super_blkno(sb, i);
                if (backup_blkno == blkno)
                        return;
        }

        BUG();
}

/*
 * Write super block and backups doesn't need to collaborate with journal,
 * so we don't need to lock ip_io_mutex and inode doesn't need to bea passed
 * into this function.
 */
int ocfs2_write_super_or_backup(struct ocfs2_super *osb,
                                struct buffer_head *bh)
{
        int ret = 0;

        mlog_entry_void();

        BUG_ON(buffer_jbd(bh));
        ocfs2_check_super_or_backup(osb->sb, bh->b_blocknr);

        if (ocfs2_is_hard_readonly(osb) || ocfs2_is_soft_readonly(osb)) {
                ret = -EROFS;
                goto out;
        }

        lock_buffer(bh);
        set_buffer_uptodate(bh);

        /* remove from dirty list before I/O. */
        clear_buffer_dirty(bh);

        get_bh(bh); /* for end_buffer_write_sync() */
        bh->b_end_io = end_buffer_write_sync;
        submit_bh(WRITE, bh);

        wait_on_buffer(bh);

        if (!buffer_uptodate(bh)) {
                ret = -EIO;
                put_bh(bh);
        }

out:
        mlog_exit(ret);
        return ret;
}