Fix a problem with the VN device. Specifically, the VN device can

cause a problem of spiraling death due to buffer resource limitations.
The vfs_bio code in general had little ability to handle buffer resource
management, and now it does.  Also, there are a lot more knobs for tuning the
vfs_bio code now.  The knobs came free because of the need that there
always be some immediately available buffers (non-delayed or locked) for
use.  Note that the buffer cache code is much less likely to get bogged
down with lots of delayed writes, even more so than before.

1 files changed, 6 insertions, 0 deletions

diff --git a/sys/gnu/fs/ext2fs/ext2_linux_ialloc.c b/sys/gnu/fs/ext2fs/ext2_linux_ialloc.c
index c20770b..c93c20e 100644
--- a/sys/gnu/fs/ext2fs/ext2_linux_ialloc.c
+++ b/sys/gnu/fs/ext2fs/ext2_linux_ialloc.c
@@ -53,6 +53,7 @@
  */
 void mark_buffer_dirty(struct buf *bh)
 {
+	numdirtybuffers++;
 	bh->b_flags |= B_DELWRI;
 	bh->b_flags &= ~(B_READ | B_ERROR);
 } 
@@ -62,6 +63,11 @@ void mark_buffer_dirty(struct buf *bh)
  */
 int ll_w_block(struct buf * bp, int waitfor)
 {
+	if (bp->b_flags & B_DELWRI) {
+		--numdirtybuffers;
+		if (needsbuffer)
+			vfs_bio_need_satisfy();
+	}
 	bp->b_flags &= ~(B_READ|B_DONE|B_ERROR|B_DELWRI);
 	bp->b_flags |= B_WRITEINPROG;
 	bp->b_vp->v_numoutput++;