xref: /csrg-svn/sys/ufs/lfs/lfs_bio.c (revision 54621)

/*
 * Copyright (c) 1991 Regents of the University of California.
 * All rights reserved.
 *
 * %sccs.include.redist.c%
 *
 *	@(#)lfs_bio.c	7.13 (Berkeley) 07/02/92
 */

#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	locked_queue_count;		/* XXX Count of locked-down buffers. */

int
lfs_bwrite(ap)
	struct vop_bwrite_args /* {
		struct buf *a_bp;
	} */ *ap;
{
	register struct buf *bp = ap->a_bp;
	int s;
#ifdef VERBOSE
printf("lfs_bwrite\n");
#endif
	/*
	 * 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.
	 */
	if (!(bp->b_flags & B_LOCKED)) {
		++locked_queue_count;
		bp->b_flags |= B_DELWRI | B_LOCKED;
		bp->b_flags &= ~(B_READ | B_DONE | 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;
	struct mount *omp;

	/* 1M in a 4K file system. */
	if (locked_queue_count < 256)
		return;
	mp = rootfs;
	do {
		/*
		 * The lock check below is to avoid races with mount
		 * and unmount.
		 */
		if (mp->mnt_stat.f_type == MOUNT_LFS &&
		    (mp->mnt_flag & (MNT_MLOCK|MNT_RDONLY|MNT_MPBUSY)) == 0 &&
		    !vfs_busy(mp)) {
			/*
			 * 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.
			 */
			locked_queue_count = 0;
			lfs_segwrite(mp, 0);
			omp = mp;
			mp = mp->mnt_next;
			vfs_unbusy(omp);
		} else
			mp = mp->mnt_next;
	} while (mp != rootfs);
}