PERFORCE change 169688 for review

[Aditya Sarawgi]

http://p4web.freebsd.org/chv.cgi?CH=169688

Change 169688 by truncs at aditya on 2009/10/22 18:25:31

	- Cache dp->i_offset in the local 'i_offset' variable for use in loop
	  	indexes so directory lookup becomes shared lock safe.  In the modifying
	 	 cases an exclusive lock is held here so the commit routine may
	  	rely on the state of i_offset.
		- Similarly handle i_diroff by fetching at the start and setting only once
	  	the operation is complete.  Without the exclusive lock these are only
	  	considered hints.
		- Assert that an exclusive lock is held when we're preparing for a commit
	  	routine.
		- Honor the lock type request from lookup instead of always using exclusive
	  	locking.

Affected files ...

.. //depot/projects/soc2009/soc_ext2fs/src/sys/fs/ext2fs/ext2_lookup.c#9 edit

Differences ...

==== //depot/projects/soc2009/soc_ext2fs/src/sys/fs/ext2fs/ext2_lookup.c#9 (text+ko) ====

@@ -298,6 +298,8 @@
 	enum {NONE, COMPACT, FOUND} slotstatus;
 	doff_t slotoffset;		/* offset of area with free space */
 	int slotsize;			/* size of area at slotoffset */
+	doff_t i_diroff;		/* cached i_diroff value */
+	doff_t i_offset;		/* cached i_offset value */
 	int slotfreespace;		/* amount of space free in slot */
 	int slotneeded;			/* size of the entry we're seeking */
 	int numdirpasses;		/* strategy for directory search */
@@ -314,6 +316,7 @@
 	int flags = cnp->cn_flags;
 	int nameiop = cnp->cn_nameiop;
 	ino_t ino;
+	int ltype;
 
 	int	DIRBLKSIZ = VTOI(ap->a_dvp)->i_e2fs->e2fs_bsize;
 
@@ -333,6 +336,7 @@
 	 * case it doesn't already exist.
 	 */
 	ino = 0;
+	i_diroff = dp->i_diroff;
 	slotstatus = FOUND;
 	slotfreespace = slotsize = slotneeded = 0;
 	if ((nameiop == CREATE || nameiop == RENAME) &&
@@ -356,34 +360,34 @@
 	 * of simplicity.
 	 */
 	bmask = VFSTOEXT2(vdp->v_mount)->um_mountp->mnt_stat.f_iosize - 1;
-	if (nameiop != LOOKUP || dp->i_diroff == 0 ||
-	    dp->i_diroff > dp->i_size) {
+	if (nameiop != LOOKUP || i_diroff == 0 ||
+	    i_diroff > dp->i_size) {
 		entryoffsetinblock = 0;
-		dp->i_offset = 0;
+		i_offset = 0;
 		numdirpasses = 1;
 	} else {
-		dp->i_offset = dp->i_diroff;
-		if ((entryoffsetinblock = dp->i_offset & bmask) &&
-		    (error = ext2_blkatoff(vdp, (off_t)dp->i_offset, NULL,
+		i_offset = i_diroff;
+		if ((entryoffsetinblock = i_offset & bmask) &&
+		    (error = ext2_blkatoff(vdp, (off_t)i_offset, NULL,
 		    &bp)))
 			return (error);
 		numdirpasses = 2;
 		nchstats.ncs_2passes++;
 	}
-	prevoff = dp->i_offset;
+	prevoff = i_offset;
 	endsearch = roundup2(dp->i_size, DIRBLKSIZ);
 	enduseful = 0;
 
 searchloop:
-	while (dp->i_offset < endsearch) {
+	while (i_offset < endsearch) {
 		/*
 		 * If necessary, get the next directory block.
 		 */
-		if ((dp->i_offset & bmask) == 0) {
+		if ((i_offset & bmask) == 0) {
 			if (bp != NULL)
 				brelse(bp);
 			if ((error =
-			    ext2_blkatoff(vdp, (off_t)dp->i_offset, NULL,
+			    ext2_blkatoff(vdp, (off_t)i_offset, NULL,
 			    &bp)) != 0)
 				return (error);
 			entryoffsetinblock = 0;
@@ -409,9 +413,9 @@
 		if (ep->e2d_reclen == 0 ||
 		    (dirchk && ext2_dirbadentry(vdp, ep, entryoffsetinblock))) {
 			int i;
-			ext2_dirbad(dp, dp->i_offset, "mangled entry");
+			ext2_dirbad(dp, i_offset, "mangled entry");
 			i = DIRBLKSIZ - (entryoffsetinblock & (DIRBLKSIZ - 1));
-			dp->i_offset += i;
+			i_offset += i;
 			entryoffsetinblock += i;
 			continue;
 		}
@@ -430,15 +434,15 @@
 			if (size > 0) {
 				if (size >= slotneeded) {
 					slotstatus = FOUND;
-					slotoffset = dp->i_offset;
+					slotoffset = i_offset;
 					slotsize = ep->e2d_reclen;
 				} else if (slotstatus == NONE) {
 					slotfreespace += size;
 					if (slotoffset == -1)
-						slotoffset = dp->i_offset;
+						slotoffset = i_offset;
 					if (slotfreespace >= slotneeded) {
 						slotstatus = COMPACT;
-						slotsize = dp->i_offset +
+						slotsize = i_offset +
 						      ep->e2d_reclen - slotoffset;
 					}
 				}
@@ -462,11 +466,11 @@
 				goto found;
 			}
 		}
-		prevoff = dp->i_offset;
-		dp->i_offset += ep->e2d_reclen;
+		prevoff = i_offset;
+		i_offset += ep->e2d_reclen;
 		entryoffsetinblock += ep->e2d_reclen;
 		if (ep->e2d_ino)
-			enduseful = dp->i_offset;
+			enduseful = i_offset;
 	}
 /* notfound: */
 	/*
@@ -475,10 +479,11 @@
 	 */
 	if (numdirpasses == 2) {
 		numdirpasses--;
-		dp->i_offset = 0;
-		endsearch = dp->i_diroff;
+		i_offset = 0;
+		endsearch = i_diroff;
 		goto searchloop;
 	}
+	dp->i_offset = i_offset;
 	if (bp != NULL)
 		brelse(bp);
 	/*
@@ -547,7 +552,7 @@
 	 */
 	if (entryoffsetinblock + EXT2_DIR_REC_LEN(ep->e2d_namlen)
 		> dp->i_size) {
-		ext2_dirbad(dp, dp->i_offset, "i_size too small");
+		ext2_dirbad(dp, i_offset, "i_size too small");
 		dp->i_size = entryoffsetinblock+EXT2_DIR_REC_LEN(ep->e2d_namlen);
 		dp->i_flag |= IN_CHANGE | IN_UPDATE;
 	}
@@ -559,8 +564,8 @@
 	 * in the cache as to where the entry was found.
 	 */
 	if ((flags & ISLASTCN) && nameiop == LOOKUP)
-		dp->i_diroff = dp->i_offset &~ (DIRBLKSIZ - 1);
-
+		dp->i_diroff = i_offset &~ (DIRBLKSIZ - 1);
+	dp->i_offset = i_offset;
 	/*
 	 * If deleting, and at end of pathname, return
 	 * parameters which can be used to remove file.
@@ -650,14 +655,26 @@
 	 */
 	pdp = vdp;
 	if (flags & ISDOTDOT) {
+		ltype = VOP_ISLOCKED(pdp);
 		VOP_UNLOCK(pdp, 0);	/* race to get the inode */
 		error = VFS_VGET(vdp->v_mount, ino, LK_EXCLUSIVE, &tdp);
-		vn_lock(pdp, LK_EXCLUSIVE | LK_RETRY);
+		vn_lock(pdp, ltype | LK_RETRY);
 		if (error != 0)
 			return (error);
 		*vpp = tdp;
 	} else if (dp->i_number == ino) {
 		VREF(vdp);	/* we want ourself, ie "." */
+		/*
+		 * When we lookup "." we still can be asked to lock it
+		 * differently.
+		 */
+		ltype = cnp->cn_lkflags & LK_TYPE_MASK;
+		if (ltype != VOP_ISLOCKED(vdp)) {
+			if (ltype == LK_EXCLUSIVE)
+				vn_lock(vdp, LK_UPGRADE | LK_RETRY);
+			else /* if (ltype == LK_SHARED) */
+				vn_lock(vdp, LK_DOWNGRADE | LK_RETRY);
+		}
 		*vpp = vdp;
 	} else {
 		if ((error = VFS_VGET(vdp->v_mount, ino, LK_EXCLUSIVE,