svn commit: r361875 - head/sys/ufs/ffs

[Kirk McKusick]

Author: mckusick
Date: Sat Jun  6 20:17:56 2020
New Revision: 361875
URL: https://svnweb.freebsd.org/changeset/base/361875

Log:
  Clear the IN_SIZEMOD and IN_IBLKDATA flags only when doing a
  synchronous inode update.
  
  The IN_SIZEMOD and IN_IBLKDATA flags indicate changes to the
  file size and block pointer fields in the inode. When these
  fields have been changed, the fsync() and fsyncdata() system
  calls must write the inode to ensure their semantics that the
  file is on stable store.
  
  The IN_SIZEMOD and IN_IBLKDATA flags cannot be cleared until
  a synchronous write of the inode is done. If they are cleared
  on an asynchronous write, then the inode may not yet have been
  written to the disk when an fsync() or fsyncdata() call is done.
  Absent these flags, these calls would not know that they needed
  to write the inode. Thus, these flags only can be cleared on
  synchronous writes of the inode. Since the inode will be locked
  for the duration of the I/O that writes it to disk, no fsync()
  or fsyncdata() will be able to run before the on-disk inode
  is complete.
  
  Reviewed by: kib
  MFC with: -r361785
  Differential revision:  https://reviews.freebsd.org/D25072

Modified:
  head/sys/ufs/ffs/ffs_inode.c

Modified: head/sys/ufs/ffs/ffs_inode.c
==============================================================================
--- head/sys/ufs/ffs/ffs_inode.c	Sat Jun  6 18:56:40 2020	(r361874)
+++ head/sys/ufs/ffs/ffs_inode.c	Sat Jun  6 20:17:56 2020	(r361875)
@@ -94,7 +94,27 @@ ffs_update(vp, waitfor)
 	ip = VTOI(vp);
 	if ((ip->i_flag & IN_MODIFIED) == 0 && waitfor == 0)
 		return (0);
-	ip->i_flag &= ~(IN_LAZYACCESS | IN_LAZYMOD | IN_MODIFIED | IN_IBLKDATA);
+	ip->i_flag &= ~(IN_LAZYACCESS | IN_LAZYMOD | IN_MODIFIED);
+	/*
+	 * The IN_SIZEMOD and IN_IBLKDATA flags indicate changes to the
+	 * file size and block pointer fields in the inode. When these
+	 * fields have been changed, the fsync() and fsyncdata() system 
+	 * calls must write the inode to ensure their semantics that the 
+	 * file is on stable store.
+	 *
+	 * The IN_SIZEMOD and IN_IBLKDATA flags cannot be cleared until
+	 * a synchronous write of the inode is done. If they are cleared
+	 * on an asynchronous write, then the inode may not yet have been
+	 * written to the disk when an fsync() or fsyncdata() call is done.
+	 * Absent these flags, these calls would not know that they needed
+	 * to write the inode. Thus, these flags only can be cleared on
+	 * synchronous writes of the inode. Since the inode will be locked
+	 * for the duration of the I/O that writes it to disk, no fsync()
+	 * or fsyncdata() will be able to run before the on-disk inode
+	 * is complete.
+	 */
+	if (waitfor)
+		ip->i_flag &= ~(IN_SIZEMOD | IN_IBLKDATA);
 	fs = ITOFS(ip);
 	if (fs->fs_ronly && ITOUMP(ip)->um_fsckpid == 0)
 		return (0);