jfs: makes diUnmount/diMount in jfs_mount_rw atomic

jfs_mount_rw can call diUnmount and then diMount. These calls change the
imap pointer. Between these two calls there may be calls of function
jfs_lookup(). The jfs_lookup() function calls jfs_iget(), which, in turn
calls diRead(). The latter references the imap pointer. That may cause
diRead() to refer to a pointer freed in diUnmount().  This commit makes
the calls to diUnmount()/diMount() atomic so that nothing will read the
imap pointer until the whole remount is completed.

Signed-off-by: Oleg Kanatov <okanatov@gmail.com>
Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>

diff --git a/fs/jfs/jfs_imap.c b/fs/jfs/jfs_imap.c
index 799d383..390cbfc 100644 (file)
--- a/fs/jfs/jfs_imap.c
+++ b/fs/jfs/jfs_imap.c
@@ -310,8 +310,8 @@ int diRead(struct inode *ip)
        iagno = INOTOIAG(ip->i_ino);
 
        /* read the iag */
-       imap = JFS_IP(ipimap)->i_imap;
        IREAD_LOCK(ipimap, RDWRLOCK_IMAP);
+       imap = JFS_IP(ipimap)->i_imap;
        rc = diIAGRead(imap, iagno, &mp);
        IREAD_UNLOCK(ipimap);
        if (rc) {

diff --git a/fs/jfs/jfs_mount.c b/fs/jfs/jfs_mount.c
index 48d1f70..b83aae5 100644 (file)
--- a/fs/jfs/jfs_mount.c
+++ b/fs/jfs/jfs_mount.c
@@ -234,11 +234,15 @@ int jfs_mount_rw(struct super_block *sb, int remount)
 
                truncate_inode_pages(sbi->ipimap->i_mapping, 0);
                truncate_inode_pages(sbi->ipbmap->i_mapping, 0);
+
+               IWRITE_LOCK(sbi->ipimap, RDWRLOCK_IMAP);
                diUnmount(sbi->ipimap, 1);
                if ((rc = diMount(sbi->ipimap))) {
+                       IWRITE_UNLOCK(sbi->ipimap);
                        jfs_err("jfs_mount_rw: diMount failed!");
                        return rc;
                }
+               IWRITE_UNLOCK(sbi->ipimap);
 
                dbUnmount(sbi->ipbmap, 1);
                if ((rc = dbMount(sbi->ipbmap))) {