When all layers support file handles, we support encoding non-decodable
file handles (a.k.a. fid) even with nfs_export=off.
When file handles do not need to be decoded, we do not need to copy up
redirected lower directories on encode, and we encode also non-indexed
upper with lower file handle, so fid will not change on copy up.
This enables reporting fanotify events with file handles on overlayfs
with default config/mount options.
Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
---
fs/overlayfs/export.c | 26 ++++++++++++++++++++------
fs/overlayfs/inode.c | 2 +-
fs/overlayfs/overlayfs.h | 1 +
fs/overlayfs/ovl_entry.h | 1 +
fs/overlayfs/super.c | 9 +++++++++
5 files changed, 32 insertions(+), 7 deletions(-)
diff --git a/fs/overlayfs/export.c b/fs/overlayfs/export.c
index 35680b6e175b..6d54f3fc24c5 100644
--- a/fs/overlayfs/export.c
+++ b/fs/overlayfs/export.c
@@ -174,28 +174,37 @@ static int ovl_connect_layer(struct dentry *dentry)
* U = upper file handle
* L = lower file handle
*
- * (*) Connecting an overlay dir from real lower dentry is not always
+ * (*) Decoding a connected overlay dir from real lower dentry is not always
* possible when there are redirects in lower layers and non-indexed merge dirs.
* To mitigate those case, we may copy up the lower dir ancestor before encode
- * a lower dir file handle.
+ * of a decodable file handle for non-upper dir.
*
* Return 0 for upper file handle, > 0 for lower file handle or < 0 on error.
*/
static int ovl_check_encode_origin(struct dentry *dentry)
{
struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
+ bool decodable = ofs->config.nfs_export;
+
+ /* Lower file handle for non-upper non-decodable */
+ if (!ovl_dentry_upper(dentry) && !decodable)
+ return 0;
/* Upper file handle for pure upper */
if (!ovl_dentry_lower(dentry))
return 0;
/*
- * Upper file handle for non-indexed upper.
- *
* Root is never indexed, so if there's an upper layer, encode upper for
* root.
*/
- if (ovl_dentry_upper(dentry) &&
+ if (dentry == dentry->d_sb->s_root)
+ return 0;
+
+ /*
+ * Upper decodable file handle for non-indexed upper.
+ */
+ if (ovl_dentry_upper(dentry) && decodable &&
!ovl_test_flag(OVL_INDEX, d_inode(dentry)))
return 0;
@@ -205,7 +214,7 @@ static int ovl_check_encode_origin(struct dentry *dentry)
* ovl_connect_layer() will try to make origin's layer "connected" by
* copying up a "connectable" ancestor.
*/
- if (d_is_dir(dentry) && ovl_upper_mnt(ofs))
+ if (d_is_dir(dentry) && ovl_upper_mnt(ofs) && decodable)
return ovl_connect_layer(dentry);
/* Lower file handle for indexed and non-upper dir/non-dir */
@@ -876,3 +885,8 @@ const struct export_operations ovl_export_operations = {
.get_name = ovl_get_name,
.get_parent = ovl_get_parent,
};
+
+/* encode_fh() encodes non-decodable file handles with nfs_export=off */
+const struct export_operations ovl_export_fid_operations = {
+ .encode_fh = ovl_encode_fh,
+};
diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index a63e57447be9..c1c9ff62caad 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -1311,7 +1311,7 @@ static bool ovl_hash_bylower(struct super_block *sb, struct dentry *upper,
return false;
/* No, if non-indexed upper with NFS export */
- if (sb->s_export_op && upper)
+ if (ofs->config.nfs_export && upper)
return false;
/* Otherwise, hash by lower inode for fsnotify */
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index 488bd14c2ed8..453610fb9bf9 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -799,6 +799,7 @@ int ovl_set_origin(struct ovl_fs *ofs, struct dentry *lower,
/* export.c */
extern const struct export_operations ovl_export_operations;
+extern const struct export_operations ovl_export_fid_operations;
/* super.c */
int ovl_fill_super(struct super_block *sb, struct fs_context *fc);
diff --git a/fs/overlayfs/ovl_entry.h b/fs/overlayfs/ovl_entry.h
index e999c73fb0c3..7a5196c94d75 100644
--- a/fs/overlayfs/ovl_entry.h
+++ b/fs/overlayfs/ovl_entry.h
@@ -82,6 +82,7 @@ struct ovl_fs {
const struct cred *creator_cred;
bool tmpfile;
bool noxattr;
+ bool nofh;
/* Did we take the inuse lock? */
bool upperdir_locked;
bool workdir_locked;
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 0ec37bb597f8..7234810a4b54 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -400,6 +400,7 @@ static int ovl_lower_dir(const char *name, struct path *path,
pr_warn("fs on '%s' does not support file handles, falling back to index=off,nfs_export=off.\n",
name);
}
+ ofs->nofh |= !fh_type;
/*
* Decoding origin file handle is required for persistent st_ino.
* Without persistent st_ino, xino=auto falls back to xino=off.
@@ -818,6 +819,7 @@ static int ovl_make_workdir(struct super_block *sb, struct ovl_fs *ofs,
ofs->config.index = false;
pr_warn("upper fs does not support file handles, falling back to index=off.\n");
}
+ ofs->nofh |= !fh_type;
/* Check if upper fs has 32bit inode numbers */
if (fh_type != FILEID_INO32_GEN)
@@ -1452,8 +1454,15 @@ int ovl_fill_super(struct super_block *sb, struct fs_context *fc)
ofs->config.nfs_export = false;
}
+ /*
+ * Support encoding decodable file handles with nfs_export=on
+ * and encoding non-decodable file handles with nfs_export=off
+ * if all layers support file handles.
+ */
if (ofs->config.nfs_export)
sb->s_export_op = &ovl_export_operations;
+ else if (!ofs->nofh)
+ sb->s_export_op = &ovl_export_fid_operations;
/* Never override disk quota limits or use reserved space */
cap_lower(cred->cap_effective, CAP_SYS_RESOURCE);
--
2.34.1
