usr/src/sys/ufs/lfs/lfs_bio.c

/*
 * Copyright (c) 1991 Regents of the University of California.
 * All rights reserved.
 *
 * %sccs.include.redist.c%
 *
 *      @(#)lfs_bio.c   7.17 (Berkeley) %G%
 */

#include <sys/param.h>
#include <sys/proc.h>
#include <sys/buf.h>
#include <sys/vnode.h>
#include <sys/resourcevar.h>
#include <sys/mount.h>

#include <ufs/ufs/quota.h>
#include <ufs/ufs/inode.h>
#include <ufs/ufs/ufsmount.h>

#include <ufs/lfs/lfs.h>
#include <ufs/lfs/lfs_extern.h>

/*
 * LFS block write function.
 *
 * XXX
 * No write cost accounting is done.
 * This is almost certainly wrong for synchronous operations and NFS.
 */
int     lfs_allclean_wakeup;            /* Cleaner wakeup address. */
int     locked_queue_count;             /* XXX Count of locked-down buffers. */
int     lfs_writing;                    /* Set if already kicked off a writer
                                           because of buffer space */
#define WRITE_THRESHHOLD        ((nbuf >> 2) - 10)
#define WAIT_THRESHHOLD         ((nbuf >> 1) - 10)

int
lfs_bwrite(ap)
        struct vop_bwrite_args /* {
                struct buf *a_bp;
        } */ *ap;
{
        register struct buf *bp = ap->a_bp;
        struct lfs *fs;
        struct inode *ip;
        int s;

        /*
         * Set the delayed write flag and use reassignbuf to move the buffer
         * from the clean list to the dirty one.
         *
         * Set the B_LOCKED flag and unlock the buffer, causing brelse to move
         * the buffer onto the LOCKED free list.  This is necessary, otherwise
         * getnewbuf() would try to reclaim the buffers using bawrite, which
         * isn't going to work.
         *
         * XXX we don't let meta-data writes run out of space because they can
         * come from the segment writer.  We need to make sure that there is
         * enough space reserved so that there's room to write meta-data
         * blocks.
         */
        if (!(bp->b_flags & B_LOCKED)) {
                fs = VFSTOUFS(bp->b_vp->v_mount)->um_lfs;
                if (!LFS_FITS(fs, fsbtodb(fs, 1)) && !IS_IFILE(bp) &&
                    bp->b_lblkno > 0) {
                        brelse(bp);
                        wakeup(&lfs_allclean_wakeup);
                        return (ENOSPC);
                }
                ip = VTOI((bp)->b_vp);
                if (!(ip->i_flag & IMOD))
                        ++fs->lfs_uinodes;
                ip->i_flag |= IMOD | ICHG | IUPD;                       \
                fs->lfs_avail -= fsbtodb(fs, 1);
                ++locked_queue_count;
                bp->b_flags |= B_DELWRI | B_LOCKED;
                bp->b_flags &= ~(B_READ | B_ERROR);
                s = splbio();
                reassignbuf(bp, bp->b_vp);
                splx(s);
        }
        brelse(bp);
        return (0);
}

/*
 * XXX
 * This routine flushes buffers out of the B_LOCKED queue when LFS has too
 * many locked down.  Eventually the pageout daemon will simply call LFS
 * when pages need to be reclaimed.  Note, we have one static count of locked
 * buffers, so we can't have more than a single file system.  To make this
 * work for multiple file systems, put the count into the mount structure.
 */
void
lfs_flush()
{
        register struct mount *mp;

        if (lfs_writing)
                return;
        lfs_writing = 1;
        mp = rootfs;
        do {
                /* The lock check below is to avoid races with unmount. */
                if (mp->mnt_stat.f_type == MOUNT_LFS &&
                    (mp->mnt_flag & (MNT_MLOCK|MNT_RDONLY|MNT_UNMOUNT)) == 0 &&
                    !((((struct ufsmount *)mp->mnt_data))->ufsmount_u.lfs)->lfs_dirops ) {
                        /*
                         * We set the queue to 0 here because we are about to
                         * write all the dirty buffers we have.  If more come
                         * in while we're writing the segment, they may not
                         * get written, so we want the count to reflect these
                         * new writes after the segwrite completes.
                         */
                        lfs_segwrite(mp, 0);
                }
                mp = mp->mnt_next;
        } while (mp != rootfs);
        lfs_writing = 0;
}

int
lfs_check(vp, blkno)
        struct vnode *vp;
        daddr_t blkno;
{
        extern int lfs_allclean_wakeup;
        int error;

        if (incore(vp, blkno))
                return (0);
        if (locked_queue_count > WRITE_THRESHHOLD)
                lfs_flush();
        if (locked_queue_count > WAIT_THRESHHOLD)
                error = tsleep(&lfs_allclean_wakeup, PCATCH | PUSER,
                    "buffers", NULL);
        return (error);
}