When we're given a remount request, we likely have some mount options
that will be changed. If the superblock is shared, however, we can't
allow those new options to be applied without affecting every mount
that's associated with this superblock. Track the number of mounts
associated with the superblock, and fail any remount attempts
that involve a shared superblock.
Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
---
fs/nfs/client.c | 1 +
fs/nfs/super.c | 15 +++++++++++++--
include/linux/nfs_fs_sb.h | 1 +
3 files changed, 15 insertions(+), 2 deletions(-)
diff --git a/fs/nfs/client.c b/fs/nfs/client.c
index c5c0175..950f4d2 100644
--- a/fs/nfs/client.c
+++ b/fs/nfs/client.c
@@ -828,6 +828,7 @@ static struct nfs_server *nfs_alloc_server(void)
init_waitqueue_head(&server->active_wq);
atomic_set(&server->active, 0);
+ atomic_set(&server->mounts, 0);
server->io_stats = nfs_alloc_iostats();
if (!server->io_stats) {
diff --git a/fs/nfs/super.c b/fs/nfs/super.c
index b49f90f..f080f1e 100644
--- a/fs/nfs/super.c
+++ b/fs/nfs/super.c
@@ -592,6 +592,7 @@ static void nfs_umount_begin(struct vfsmount *vfsmnt, int flags)
struct nfs_server *server = NFS_SB(vfsmnt->mnt_sb);
struct rpc_clnt *rpc;
+ atomic_dec(&server->mounts);
if (!(flags & MNT_FORCE))
return;
/* -EIO all pending I/O */
@@ -1359,6 +1360,14 @@ nfs_remount(struct super_block *sb, int *flags, char *raw_data)
struct nfs4_mount_data *options4 = (struct nfs4_mount_data *)raw_data;
/*
+ * We're presumably remounting to change some mount options. Fail
+ * the mount if the superblock is shared, since the change would
+ * affect all the mounts sharing this superblock
+ */
+ if (atomic_read(&nfss->mounts) > 1)
+ return -EBUSY;
+
+ /*
* Userspace mount programs that send binary options generally send
* them populated with default values. We have no way to know which
* ones were explicitly specified. Fall back to legacy behavior and
@@ -1615,7 +1624,7 @@ static int nfs_get_sb(struct file_system_type *fs_type,
if (s->s_fs_info != server) {
nfs_free_server(server);
- server = NULL;
+ server = (struct nfs_server *) s->s_fs_info;
}
if (!s->s_root) {
@@ -1633,6 +1642,7 @@ static int nfs_get_sb(struct file_system_type *fs_type,
if (error)
goto error_splat_root;
+ atomic_inc(&server->mounts);
s->s_flags |= MS_ACTIVE;
mnt->mnt_sb = s;
mnt->mnt_root = mntroot;
@@ -2001,7 +2011,7 @@ static int nfs4_get_sb(struct file_system_type *fs_type,
if (s->s_fs_info != server) {
nfs_free_server(server);
- server = NULL;
+ server = (struct nfs_server *) s->s_fs_info;
}
if (!s->s_root) {
@@ -2015,6 +2025,7 @@ static int nfs4_get_sb(struct file_system_type *fs_type,
goto error_splat_super;
}
+ atomic_inc(&server->mounts);
s->s_flags |= MS_ACTIVE;
mnt->mnt_sb = s;
mnt->mnt_root = mntroot;
diff --git a/include/linux/nfs_fs_sb.h b/include/linux/nfs_fs_sb.h
index 3423c67..c98f522 100644
--- a/include/linux/nfs_fs_sb.h
+++ b/include/linux/nfs_fs_sb.h
@@ -117,6 +117,7 @@ struct nfs_server {
atomic_t active; /* Keep trace of any activity to this server */
wait_queue_head_t active_wq; /* Wait for any activity to stop */
+ atomic_t mounts; /* # of mounts sharing this sb */
};
/* Server capabilities */
--
1.5.3.6
--
To unsubscribe from this list: send the line "unsubscribe linux-nfs" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
