Re: readdir returns d_type=DT_UNKNOWN to overlay exported dir (NFSv3)

[Amir Goldstein <amir73il@gmail.com>]

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On Thu, Mar 15, 2018 at 8:40 PM, Amir Goldstein <amir73il@gmail.com> wrote:
> On Thu, Mar 15, 2018 at 4:30 PM, Eddie Horng <eddiehorng.tw@gmail.com> wrote:
[...]
> The problem *is* with nfsd+overlayfs, because nfsd verifies
> in compose_entry_fh() that (dchild->d_inode->i_ino == ino), but it is not.
> In that case, encode_entryplus_baggage() falls back to encoding xdr_zero.
> In overlayfs stat.st_ino is consistent with readdir d_ino since kernel version
> v4.15 and only for all layers on the same fs.
>
> However, there is no guaranty that inode->i_ino is the same as stat.st_ino.
> Overlayfs exposes only stat.st_ino to user (as well as readdir d_ino), but
> never (to my knowledge) does it expose inode->i_ino.
>
> There was a nfsd fix for a somewhat similar problem that went into v4.16-rc1:
> 76c479480b9a nfsd: encode stat->mtime for getattr instead of inode->i_mtime
>
> The solution to the problem is to either convert all references of
> nfsd to i_inode
> with references to st_ino, or make sure to set inode->i_ino correctly for
> overlayfs inodes.
>
> From first glimps, the change in nfsd looks non trivial.
> The change to overlayfs seems doable, but didn't look closely yet.
> Will try to come up with test patch for you.
>

Eddie,

Please try this patch. It worked for me.

Thanks,
Amir.

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From 5dfe75eaf1aec080d110df343aa339ad7b816670 Mon Sep 17 00:00:00 2001
From: Amir Goldstein <amir73il@gmail.com>
Date: Thu, 15 Mar 2018 23:39:01 +0200
Subject: [PATCH] ovl: set i_ino to the value of st_ino for NFS export

When NFS export is enabled and d_ino is consistent with st_ino
(samefs), set the same value to i_ino, because nfsd readdirplus
compares d_ino values to i_ino values of child entries. When called
from ovl_new_inode(), ino arg is 0, so i_ino will be updated to real
upper inode i_ino on ovl_inode_init() or ovl_inode_update().

Reported-by: Eddie Horng <eddiehorng.tw@gmail.com>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
---
 fs/overlayfs/inode.c | 21 +++++++++++++++++----
 fs/overlayfs/util.c  |  8 +++++++-
 2 files changed, 24 insertions(+), 5 deletions(-)

diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index 3b1bd469accd..4689716f23d8 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -459,9 +459,20 @@ static inline void ovl_lockdep_annotate_inode_mutex_key(struct inode *inode)
 #endif
 }
 
-static void ovl_fill_inode(struct inode *inode, umode_t mode, dev_t rdev)
+static void ovl_fill_inode(struct inode *inode, umode_t mode, dev_t rdev,
+			   unsigned long ino)
 {
-	inode->i_ino = get_next_ino();
+	/*
+	 * When NFS export is enabled and d_ino is consistent with st_ino
+	 * (samefs), set the same value to i_ino, because nfsd readdirplus
+	 * compares d_ino values to i_ino values of child entries. When called
+	 * from ovl_new_inode(), ino arg is 0, so i_ino will be updated to real
+	 * upper inode i_ino on ovl_inode_init() or ovl_inode_update().
+	 */
+	if (inode->i_sb->s_export_op && ovl_same_sb(inode->i_sb))
+		inode->i_ino = ino;
+	else
+		inode->i_ino = get_next_ino();
 	inode->i_mode = mode;
 	inode->i_flags |= S_NOCMTIME;
 #ifdef CONFIG_FS_POSIX_ACL
@@ -597,7 +608,7 @@ struct inode *ovl_new_inode(struct super_block *sb, umode_t mode, dev_t rdev)
 
 	inode = new_inode(sb);
 	if (inode)
-		ovl_fill_inode(inode, mode, rdev);
+		ovl_fill_inode(inode, mode, rdev, 0);
 
 	return inode;
 }
@@ -710,6 +721,7 @@ struct inode *ovl_get_inode(struct super_block *sb, struct dentry *upperdentry,
 	struct inode *inode;
 	bool bylower = ovl_hash_bylower(sb, upperdentry, lowerdentry, index);
 	bool is_dir;
+	unsigned long ino = 0;
 
 	if (!realinode)
 		realinode = d_inode(lowerdentry);
@@ -748,13 +760,14 @@ struct inode *ovl_get_inode(struct super_block *sb, struct dentry *upperdentry,
 		if (!is_dir)
 			nlink = ovl_get_nlink(lowerdentry, upperdentry, nlink);
 		set_nlink(inode, nlink);
+		ino = key->i_ino;
 	} else {
 		/* Lower hardlink that will be broken on copy up */
 		inode = new_inode(sb);
 		if (!inode)
 			goto out_nomem;
 	}
-	ovl_fill_inode(inode, realinode->i_mode, realinode->i_rdev);
+	ovl_fill_inode(inode, realinode->i_mode, realinode->i_rdev, ino);
 	ovl_inode_init(inode, upperdentry, lowerdentry);
 
 	if (upperdentry && ovl_is_impuredir(upperdentry))
diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c
index 930784a26623..493f9b76fbf6 100644
--- a/fs/overlayfs/util.c
+++ b/fs/overlayfs/util.c
@@ -279,12 +279,16 @@ void ovl_dentry_set_redirect(struct dentry *dentry, const char *redirect)
 void ovl_inode_init(struct inode *inode, struct dentry *upperdentry,
 		    struct dentry *lowerdentry)
 {
+	struct inode *realinode = d_inode(upperdentry ?: lowerdentry);
+
 	if (upperdentry)
 		OVL_I(inode)->__upperdentry = upperdentry;
 	if (lowerdentry)
 		OVL_I(inode)->lower = igrab(d_inode(lowerdentry));
 
-	ovl_copyattr(d_inode(upperdentry ?: lowerdentry), inode);
+	ovl_copyattr(realinode, inode);
+	if (!inode->i_ino)
+		inode->i_ino = realinode->i_ino;
 }
 
 void ovl_inode_update(struct inode *inode, struct dentry *upperdentry)
@@ -299,6 +303,8 @@ void ovl_inode_update(struct inode *inode, struct dentry *upperdentry)
 	smp_wmb();
 	OVL_I(inode)->__upperdentry = upperdentry;
 	if (inode_unhashed(inode)) {
+		if (!inode->i_ino)
+			inode->i_ino = upperinode->i_ino;
 		inode->i_private = upperinode;
 		__insert_inode_hash(inode, (unsigned long) upperinode);
 	}
-- 
2.7.4