Function brelse

freebsd/kern/vfs_bio.c:2609–2805

* brelse: * * Release a busy buffer and, if requested, free its resources. The * buffer will be stashed in the appropriate bufqueue[] allowing it * to be accessed later as a cache entity or reused for other purposes. */

 *	to be accessed later as a cache entity or reused for other purposes.
 */
void
brelse(struct buf *bp)
{
	struct mount *v_mnt;
	int qindex;

	/*
	 * Many functions erroneously call brelse with a NULL bp under rare
	 * error conditions. Simply return when called with a NULL bp.
	 */
	if (bp == NULL)
		return;
	CTR3(KTR_BUF, "brelse(%p) vp %p flags %X",
	    bp, bp->b_vp, bp->b_flags);
	KASSERT(!(bp->b_flags & (B_CLUSTER|B_PAGING)),
	    ("brelse: inappropriate B_PAGING or B_CLUSTER bp %p", bp));
	KASSERT((bp->b_flags & B_VMIO) != 0 || (bp->b_flags & B_NOREUSE) == 0,
	    ("brelse: non-VMIO buffer marked NOREUSE"));

	if (BUF_LOCKRECURSED(bp)) {
		/*
		 * Do not process, in particular, do not handle the
		 * B_INVAL/B_RELBUF and do not release to free list.
		 */
		BUF_UNLOCK(bp);
		return;
	}

	if (bp->b_flags & B_MANAGED) {
		bqrelse(bp);
		return;
	}

	if (LIST_EMPTY(&bp->b_dep)) {
		bp->b_flags &= ~B_IOSTARTED;
	} else {
		KASSERT((bp->b_flags & B_IOSTARTED) == 0,
		    ("brelse: SU io not finished bp %p", bp));
	}

	if ((bp->b_vflags & (BV_BKGRDINPROG | BV_BKGRDERR)) == BV_BKGRDERR) {
		BO_LOCK(bp->b_bufobj);
		bp->b_vflags &= ~BV_BKGRDERR;
		BO_UNLOCK(bp->b_bufobj);
		bdirty(bp);
	}

	if (bp->b_iocmd == BIO_WRITE && (bp->b_ioflags & BIO_ERROR) &&
	    (bp->b_flags & B_INVALONERR)) {
		/*
		 * Forced invalidation of dirty buffer contents, to be used
		 * after a failed write in the rare case that the loss of the
		 * contents is acceptable.  The buffer is invalidated and
		 * freed.
		 */
		bp->b_flags |= B_INVAL | B_RELBUF | B_NOCACHE;
		bp->b_flags &= ~(B_ASYNC | B_CACHE);
	}