buffer_head_io.c

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/* -*- 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/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"
#include "ocfs2_trace.h"

/*
 * Bits on bh->b_state used by ocfs2.
 *
 * These MUST be after the JBD2 bits.  Hence, we use BH_JBDPrivateStart.
 */
enum ocfs2_state_bits {
    BH_NeedsValidate = BH_JBDPrivateStart,
};

/* Expand the magic b_state functions */
BUFFER_FNS(NeedsValidate, needs_validate);

int ocfs2_write_block(struct ocfs2_super *osb, struct buffer_head *bh,
              struct ocfs2_caching_info *ci)
{
    int ret = 0;

    trace_ocfs2_write_block((unsigned long long)bh->b_blocknr, ci);

    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;
        mlog_errno(ret);
        goto out;
    }

    ocfs2_metadata_cache_io_lock(ci);

    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(ci, 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);
        mlog_errno(ret);
    }

    ocfs2_metadata_cache_io_unlock(ci);
out:
    return ret;
}

int ocfs2_read_blocks_sync(struct ocfs2_super *osb, u64 block,
               unsigned int nr, struct buffer_head *bhs[])
{
    int status = 0;
    unsigned int i;
    struct buffer_head *bh;

    trace_ocfs2_read_blocks_sync((unsigned long long)block, nr);

    if (!nr)
        goto bail;

    for (i = 0 ; i < nr ; i++) {
        if (bhs[i] == NULL) {
            bhs[i] = sb_getblk(osb->sb, block++);
            if (bhs[i] == NULL) {
                status = -EIO;
                mlog_errno(status);
                goto bail;
            }
        }
        bh = bhs[i];

        if (buffer_jbd(bh)) {
            trace_ocfs2_read_blocks_sync_jbd(
                    (unsigned long long)bh->b_blocknr);
            continue;
        }

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

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

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

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

        /* No need to wait on the buffer if it's managed by JBD. */
        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. */
            status = -EIO;
            put_bh(bh);
            bhs[i - 1] = NULL;
        }
    }

bail:
    return status;
}

int ocfs2_read_blocks(struct ocfs2_caching_info *ci, u64 block, int nr,
              struct buffer_head *bhs[], int flags,
              int (*validate)(struct super_block *sb,
                      struct buffer_head *bh))
{
    int status = 0;
    int i, ignore_cache = 0;
    struct buffer_head *bh;
    struct super_block *sb = ocfs2_metadata_cache_get_super(ci);

    trace_ocfs2_read_blocks_begin(ci, (unsigned long long)block, nr, flags);

    BUG_ON(!ci);
    BUG_ON((flags & OCFS2_BH_READAHEAD) &&
           (flags & OCFS2_BH_IGNORE_CACHE));

    if (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) {
        status = 0;
        goto bail;
    }

    ocfs2_metadata_cache_io_lock(ci);
    for (i = 0 ; i < nr ; i++) {
        if (bhs[i] == NULL) {
            bhs[i] = sb_getblk(sb, block++);
            if (bhs[i] == NULL) {
                ocfs2_metadata_cache_io_unlock(ci);
                status = -EIO;
                mlog_errno(status);
                goto bail;
            }
        }
        bh = bhs[i];
        ignore_cache = (flags & OCFS2_BH_IGNORE_CACHE);

        /* 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 (!ignore_cache && !ocfs2_buffer_uptodate(ci, bh)) {
            trace_ocfs2_read_blocks_from_disk(
                 (unsigned long long)bh->b_blocknr,
                 (unsigned long long)ocfs2_metadata_cache_owner(ci));
            /* We're using ignore_cache here to say
             * "go to disk" */
            ignore_cache = 1;
        }

        trace_ocfs2_read_blocks_bh((unsigned long long)bh->b_blocknr,
            ignore_cache, buffer_jbd(bh), buffer_dirty(bh));

        if (buffer_jbd(bh)) {
            continue;
        }

        if (ignore_cache) {
            if (buffer_dirty(bh)) {
                /* This should probably be a BUG, or
                 * at least return an error. */
                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(ci, 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_IGNORE_CACHE)
                && !(flags & OCFS2_BH_READAHEAD)
                && ocfs2_buffer_uptodate(ci, bh)) {
                unlock_buffer(bh);
                continue;
            }

            clear_buffer_uptodate(bh);
            get_bh(bh); /* for end_buffer_read_sync() */
            if (validate)
                set_buffer_needs_validate(bh);
            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
             * owner 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;
            }

            if (buffer_needs_validate(bh)) {
                /* We never set NeedsValidate if the
                 * buffer was held by the journal, so
                 * that better not have changed */
                BUG_ON(buffer_jbd(bh));
                clear_buffer_needs_validate(bh);
                status = validate(sb, bh);
                if (status) {
                    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. */
        ocfs2_set_buffer_uptodate(ci, bh);
    }
    ocfs2_metadata_cache_io_unlock(ci);

    trace_ocfs2_read_blocks_end((unsigned long long)block, nr,
                    flags, ignore_cache);

bail:

    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 ci 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;
    struct ocfs2_dinode *di = (struct ocfs2_dinode *)bh->b_data;

    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;
        mlog_errno(ret);
        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;
    ocfs2_compute_meta_ecc(osb->sb, bh->b_data, &di->i_check);
    submit_bh(WRITE, bh);

    wait_on_buffer(bh);

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

out:
    return ret;
}