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-rw-r--r--fs/overlayfs/Kconfig17
-rw-r--r--fs/overlayfs/ovl_entry.h1
-rw-r--r--fs/overlayfs/super.c73
3 files changed, 88 insertions, 3 deletions
diff --git a/fs/overlayfs/Kconfig b/fs/overlayfs/Kconfig
index ce6ff5a0a6e4..17032631c5cf 100644
--- a/fs/overlayfs/Kconfig
+++ b/fs/overlayfs/Kconfig
@@ -86,3 +86,20 @@ config OVERLAY_FS_NFS_EXPORT
case basis with the "nfs_export=on" mount option.
Say N unless you fully understand the consequences.
+
+config OVERLAY_FS_XINO_AUTO
+ bool "Overlayfs: auto enable inode number mapping"
+ default n
+ depends on OVERLAY_FS
+ help
+ If this config option is enabled then overlay filesystems will use
+ unused high bits in undelying filesystem inode numbers to map all
+ inodes to a unified address space. The mapped 64bit inode numbers
+ might not be compatible with applications that expect 32bit inodes.
+
+ If compatibility with applications that expect 32bit inodes is not an
+ issue, then it is safe and recommended to say Y here.
+
+ For more information, see Documentation/filesystems/overlayfs.txt
+
+ If unsure, say N.
diff --git a/fs/overlayfs/ovl_entry.h b/fs/overlayfs/ovl_entry.h
index 620bd20f9a22..41655a7d6894 100644
--- a/fs/overlayfs/ovl_entry.h
+++ b/fs/overlayfs/ovl_entry.h
@@ -18,6 +18,7 @@ struct ovl_config {
const char *redirect_mode;
bool index;
bool nfs_export;
+ int xino;
};
struct ovl_sb {
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index d7284444f404..e8551c97de51 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -51,6 +51,11 @@ module_param_named(nfs_export, ovl_nfs_export_def, bool, 0644);
MODULE_PARM_DESC(ovl_nfs_export_def,
"Default to on or off for the NFS export feature");
+static bool ovl_xino_auto_def = IS_ENABLED(CONFIG_OVERLAY_FS_XINO_AUTO);
+module_param_named(xino_auto, ovl_xino_auto_def, bool, 0644);
+MODULE_PARM_DESC(ovl_xino_auto_def,
+ "Auto enable xino feature");
+
static void ovl_entry_stack_free(struct ovl_entry *oe)
{
unsigned int i;
@@ -327,6 +332,23 @@ static const char *ovl_redirect_mode_def(void)
return ovl_redirect_dir_def ? "on" : "off";
}
+enum {
+ OVL_XINO_OFF,
+ OVL_XINO_AUTO,
+ OVL_XINO_ON,
+};
+
+static const char * const ovl_xino_str[] = {
+ "off",
+ "auto",
+ "on",
+};
+
+static inline int ovl_xino_def(void)
+{
+ return ovl_xino_auto_def ? OVL_XINO_AUTO : OVL_XINO_OFF;
+}
+
/**
* ovl_show_options
*
@@ -352,6 +374,8 @@ static int ovl_show_options(struct seq_file *m, struct dentry *dentry)
if (ofs->config.nfs_export != ovl_nfs_export_def)
seq_printf(m, ",nfs_export=%s", ofs->config.nfs_export ?
"on" : "off");
+ if (ofs->config.xino != ovl_xino_def())
+ seq_printf(m, ",xino=%s", ovl_xino_str[ofs->config.xino]);
return 0;
}
@@ -386,6 +410,9 @@ enum {
OPT_INDEX_OFF,
OPT_NFS_EXPORT_ON,
OPT_NFS_EXPORT_OFF,
+ OPT_XINO_ON,
+ OPT_XINO_OFF,
+ OPT_XINO_AUTO,
OPT_ERR,
};
@@ -399,6 +426,9 @@ static const match_table_t ovl_tokens = {
{OPT_INDEX_OFF, "index=off"},
{OPT_NFS_EXPORT_ON, "nfs_export=on"},
{OPT_NFS_EXPORT_OFF, "nfs_export=off"},
+ {OPT_XINO_ON, "xino=on"},
+ {OPT_XINO_OFF, "xino=off"},
+ {OPT_XINO_AUTO, "xino=auto"},
{OPT_ERR, NULL}
};
@@ -513,6 +543,18 @@ static int ovl_parse_opt(char *opt, struct ovl_config *config)
config->nfs_export = false;
break;
+ case OPT_XINO_ON:
+ config->xino = OVL_XINO_ON;
+ break;
+
+ case OPT_XINO_OFF:
+ config->xino = OVL_XINO_OFF;
+ break;
+
+ case OPT_XINO_AUTO:
+ config->xino = OVL_XINO_AUTO;
+ break;
+
default:
pr_err("overlayfs: unrecognized mount option \"%s\" or missing value\n", p);
return -EINVAL;
@@ -1197,9 +1239,31 @@ static int ovl_get_lower_layers(struct ovl_fs *ofs, struct path *stack,
ofs->numlower++;
}
- /* When all layers on same fs, overlay can use real inode numbers */
- if (!ofs->numlowerfs || (ofs->numlowerfs == 1 && !ofs->upper_mnt))
+ /*
+ * When all layers on same fs, overlay can use real inode numbers.
+ * With mount option "xino=on", mounter declares that there are enough
+ * free high bits in underlying fs to hold the unique fsid.
+ * If overlayfs does encounter underlying inodes using the high xino
+ * bits reserved for fsid, it emits a warning and uses the original
+ * inode number.
+ */
+ if (!ofs->numlowerfs || (ofs->numlowerfs == 1 && !ofs->upper_mnt)) {
ofs->xino_bits = 0;
+ ofs->config.xino = OVL_XINO_OFF;
+ } else if (ofs->config.xino == OVL_XINO_ON && !ofs->xino_bits) {
+ /*
+ * This is a roundup of number of bits needed for numlowerfs+1
+ * (i.e. ilog2(numlowerfs+1 - 1) + 1). fsid 0 is reserved for
+ * upper fs even with non upper overlay.
+ */
+ BUILD_BUG_ON(ilog2(OVL_MAX_STACK) > 31);
+ ofs->xino_bits = ilog2(ofs->numlowerfs) + 1;
+ }
+
+ if (ofs->xino_bits) {
+ pr_info("overlayfs: \"xino\" feature enabled using %d upper inode bits.\n",
+ ofs->xino_bits);
+ }
err = 0;
out:
@@ -1311,6 +1375,7 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
ofs->config.index = ovl_index_def;
ofs->config.nfs_export = ovl_nfs_export_def;
+ ofs->config.xino = ovl_xino_def();
err = ovl_parse_opt((char *) data, &ofs->config);
if (err)
goto out_err;
@@ -1325,7 +1390,9 @@ 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 */
- ofs->xino_bits = BITS_PER_LONG - 32;
+ if (ofs->config.xino != OVL_XINO_OFF)
+ ofs->xino_bits = BITS_PER_LONG - 32;
+
if (ofs->config.upperdir) {
if (!ofs->config.workdir) {
pr_err("overlayfs: missing 'workdir'\n");