svn commit: r333693 - head/sys/fs/msdosfs

[Kirk McKusick]

Author: mckusick
Date: Wed May 16 23:30:03 2018
New Revision: 333693
URL: https://svnweb.freebsd.org/changeset/base/333693

Log:
  Revert change made in base r171522
  (https://svnweb.freebsd.org/base?view=revision&revision=304232)
  converting clrbuf() (which clears the entire buffer) to vfs_bio_clrbuf()
  (which clears only the new pages that have been added to the buffer).
  
  Failure to properly remove pages from the buffer cache can make
  pages that appear not to need clearing to actually have bad random
  data in them. See for example base r304232
  (https://svnweb.freebsd.org/base?view=revision&revision=304232)
  which noted the need to set B_INVAL and B_NOCACHE as well as clear
  the B_CACHE flag before calling brelse() to release the buffer.
  
  Rather than trying to find all the incomplete brelse() calls, it
  is simpler, though more slightly expensive, to simply clear the
  entire buffer when it is newly allocated.
  
  PR: 213507
  Submitted by: Damjan Jovanovic
  Reviewed by:  kib

Modified:
  head/sys/fs/msdosfs/msdosfs_fat.c

Modified: head/sys/fs/msdosfs/msdosfs_fat.c
==============================================================================
--- head/sys/fs/msdosfs/msdosfs_fat.c	Wed May 16 23:10:19 2018	(r333692)
+++ head/sys/fs/msdosfs/msdosfs_fat.c	Wed May 16 23:30:03 2018	(r333693)
@@ -1082,7 +1082,7 @@ extendfile(struct denode *dep, u_long count, struct bu
 					else
 						bp->b_blkno = blkno;
 				}
-				vfs_bio_clrbuf(bp);
+				clrbuf(bp);
 				if (bpp) {
 					*bpp = bp;
 					bpp = NULL;