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Date:      Mon, 8 Apr 2019 15:20:06 +0000 (UTC)
From:      Konstantin Belousov <kib@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r346031 - head/sys/ufs/ffs
Message-ID:  <201904081520.x38FK6UA052742@repo.freebsd.org>
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Author: kib
Date: Mon Apr  8 15:20:05 2019
New Revision: 346031
URL: https://svnweb.freebsd.org/changeset/base/346031

Log:
  Handle races when remounting UFS volume from ro to rw.
  
  In particular, ensure that writers are not unleashed before SU
  structures are initialized.  Also, correctly handle MNT_ASYNC before
  this.
  
  Reported and tested by:	pho
  Reviewed by:	mckusick
  Sponsored by:	The FreeBSD Foundation
  MFC after:	1 week

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

Modified: head/sys/ufs/ffs/ffs_vfsops.c
==============================================================================
--- head/sys/ufs/ffs/ffs_vfsops.c	Mon Apr  8 14:31:07 2019	(r346030)
+++ head/sys/ufs/ffs/ffs_vfsops.c	Mon Apr  8 15:20:05 2019	(r346031)
@@ -154,7 +154,7 @@ ffs_mount(struct mount *mp)
 	struct fs *fs;
 	pid_t fsckpid = 0;
 	int error, error1, flags;
-	uint64_t mntorflags;
+	uint64_t mntorflags, saved_mnt_flag;
 	accmode_t accmode;
 	struct nameidata ndp;
 	char *fspec;
@@ -371,25 +371,40 @@ ffs_mount(struct mount *mp)
 				return (error);
 			if ((error = vn_start_write(NULL, &mp, V_WAIT)) != 0)
 				return (error);
+			error = vfs_write_suspend_umnt(mp);
+			if (error != 0)
+				return (error);
 			fs->fs_ronly = 0;
 			MNT_ILOCK(mp);
-			mp->mnt_flag &= ~MNT_RDONLY;
+			saved_mnt_flag = MNT_RDONLY;
+			if (MOUNTEDSOFTDEP(mp) && (mp->mnt_flag &
+			    MNT_ASYNC) != 0)
+				saved_mnt_flag |= MNT_ASYNC;
+			mp->mnt_flag &= ~saved_mnt_flag;
 			MNT_IUNLOCK(mp);
 			fs->fs_mtime = time_second;
 			/* check to see if we need to start softdep */
 			if ((fs->fs_flags & FS_DOSOFTDEP) &&
 			    (error = softdep_mount(devvp, mp, fs, td->td_ucred))){
-				vn_finished_write(mp);
+				fs->fs_ronly = 1;
+				MNT_ILOCK(mp);
+				mp->mnt_flag |= saved_mnt_flag;
+				MNT_IUNLOCK(mp);
+				vfs_write_resume(mp, 0);
 				return (error);
 			}
 			fs->fs_clean = 0;
 			if ((error = ffs_sbupdate(ump, MNT_WAIT, 0)) != 0) {
-				vn_finished_write(mp);
+				fs->fs_ronly = 1;
+				MNT_ILOCK(mp);
+				mp->mnt_flag |= saved_mnt_flag;
+				MNT_IUNLOCK(mp);
+				vfs_write_resume(mp, 0);
 				return (error);
 			}
 			if (fs->fs_snapinum[0] != 0)
 				ffs_snapshot_mount(mp);
-			vn_finished_write(mp);
+			vfs_write_resume(mp, 0);
 		}
 		/*
 		 * Soft updates is incompatible with "async",

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