Implement fully asynchronous partial truncation with softupdates journaling

to resolve errors which can cause corruption on recovery with the old
synchronous mechanism.

 - Append partial truncation freework structures to indirdeps while
   truncation is proceeding.  These prevent new block pointers from
   becoming valid until truncation completes and serialize truncations.
 - On completion of a partial truncate journal work waits for zeroed
   pointers to hit indirects.
 - softdep_journal_freeblocks() handles last frag allocation and last
   block zeroing.
 - vtruncbuf/ffs_page_remove moved into softdep_*_freeblocks() so it
   is only implemented in one place.
 - Block allocation failure handling moved up one level so it does not
   proceed with buf locks held.  This permits us to do more extensive
   reclaims when filesystem space is exhausted.
 - softdep_sync_metadata() is broken into two parts, the first executes
   once at the start of ffs_syncvnode() and flushes truncations and
   inode dependencies.  The second is called on each locked buf.  This
   eliminates excessive looping and rollbacks.
 - Improve the mechanism in process_worklist_item() that handles
   acquiring vnode locks for handle_workitem_remove() so that it works
   more generally and does not loop excessively over the same worklist
   items on each call.
 - Don't corrupt directories by zeroing the tail in fsck.  This is only
   done for regular files.
 - Push a fsync complete record for files that need it so the checker
   knows a truncation in the journal is no longer valid.

Discussed with:	mckusick, kib (ffs_pages_remove and ffs_truncate parts)
Tested by:	pho

1 files changed, 2 insertions, 2 deletions

diff --git a/sys/ufs/ffs/ffs_alloc.c b/sys/ufs/ffs/ffs_alloc.c
index 7f5d1b4..685b9e1 100644
--- a/sys/ufs/ffs/ffs_alloc.c
+++ b/sys/ufs/ffs/ffs_alloc.c
@@ -217,7 +217,7 @@ nospace:
 	(void) chkdq(ip, -btodb(size), cred, FORCE);
 	UFS_LOCK(ump);
 #endif
-	if (reclaimed == 0) {
+	if (reclaimed == 0 && (flags & IO_BUFLOCKED) == 0) {
 		reclaimed = 1;
 		softdep_request_cleanup(fs, ITOV(ip), cred, FLUSH_BLOCKS_WAIT);
 		goto retry;
@@ -418,7 +418,7 @@ nospace:
 	/*
 	 * no space available
 	 */
-	if (reclaimed == 0) {
+	if (reclaimed == 0 && (flags & IO_BUFLOCKED) == 0) {
 		reclaimed = 1;
 		UFS_UNLOCK(ump);
 		if (bp) {