ovl: fix some xino configurations

Fix up two bugs in the coversion to xino_mode:
1. xino=off does not always end up in disabled mode
2. xino=auto on 32bit arch should end up in disabled mode

Take a proactive approach to disabling xino on 32bit kernel:
1. Disable XINO_AUTO config during build time
2. Disable xino with a warning on mount time

As a by product, xino=on on 32bit arch also ends up in disabled mode.
We never intended to enable xino on 32bit arch and this will make the
rest of the logic simpler.

Fixes: 0f831ec85eda ("ovl: simplify ovl_same_sb() helper")
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

diff --git a/fs/overlayfs/Kconfig b/fs/overlayfs/Kconfig
index 444e2da..714c14c 100644 (file)
--- a/fs/overlayfs/Kconfig
+++ b/fs/overlayfs/Kconfig
@@ -93,6 +93,7 @@ config OVERLAY_FS_XINO_AUTO
        bool "Overlayfs: auto enable inode number mapping"
        default n
        depends on OVERLAY_FS
+       depends on 64BIT
        help
          If this config option is enabled then overlay filesystems will use
          unused high bits in undelying filesystem inode numbers to map all

diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 319fe0d..ac967f1 100644 (file)
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -1411,6 +1411,8 @@ static int ovl_get_layers(struct super_block *sb, struct ovl_fs *ofs,
                if (ofs->config.xino == OVL_XINO_ON)
                        pr_info("\"xino=on\" is useless with all layers on same fs, ignore.\n");
                ofs->xino_mode = 0;
+       } else if (ofs->config.xino == OVL_XINO_OFF) {
+               ofs->xino_mode = -1;
        } else if (ofs->config.xino == OVL_XINO_ON && ofs->xino_mode < 0) {
                /*
                 * This is a roundup of number of bits needed for encoding
@@ -1623,8 +1625,13 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
        sb->s_stack_depth = 0;
        sb->s_maxbytes = MAX_LFS_FILESIZE;
        /* Assume underlaying fs uses 32bit inodes unless proven otherwise */
-       if (ofs->config.xino != OVL_XINO_OFF)
+       if (ofs->config.xino != OVL_XINO_OFF) {
                ofs->xino_mode = BITS_PER_LONG - 32;
+               if (!ofs->xino_mode) {
+                       pr_warn("xino not supported on 32bit kernel, falling back to xino=off.\n");
+                       ofs->config.xino = OVL_XINO_OFF;
+               }
+       }
 
        /* alloc/destroy_inode needed for setting up traps in inode cache */
        sb->s_op = &ovl_super_operations;