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Groups > linux.kernel > #1412621

[PATCH] Allow d_splice_alias to accept hashed dentries

From green@linuxhacker.ru
Newsgroups linux.kernel
Subject [PATCH] Allow d_splice_alias to accept hashed dentries
Date 2016-06-03 02:10 +0200
Message-ID <rFKQx-4rb-5@gated-at.bofh.it> (permalink)
References <rFJUt-3Rl-1@gated-at.bofh.it>
Organization linux.* mail to news gateway

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From: Oleg Drokin <green@linuxhacker.ru>

The comment at the top of the function already permits it,
just take out the assetrtion and update __d_add to
be aware of this. Move the BUG_ON to d_add which is the
other user of __d_add and presumably we do not want to
allow hashed dentries as input there.

Signed-off-by: Oleg Drokin <green@linuxhacker.ru>
---
So seeing how there's only one other __d_add user, I just moved the BUG_ON
to d_add and allowed __d_add to not call _d_rehash if the dentry is
already hashed.
This seems to be working as expected and I don't see any problems with it.
Of course I am probably missing some other important consideration ;)

 fs/dcache.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/fs/dcache.c b/fs/dcache.c
index ad4a542..0e35049 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -2565,7 +2565,8 @@ static inline void __d_add(struct dentry *dentry, struct inode *inode)
 		raw_write_seqcount_end(&dentry->d_seq);
 		__fsnotify_d_instantiate(dentry);
 	}
-	_d_rehash(dentry);
+	if (d_unhashed(dentry))
+		_d_rehash(dentry);
 	if (dir)
 		end_dir_add(dir, n);
 	spin_unlock(&dentry->d_lock);
@@ -2584,6 +2585,8 @@ static inline void __d_add(struct dentry *dentry, struct inode *inode)
 
 void d_add(struct dentry *entry, struct inode *inode)
 {
+	BUG_ON(!d_unhashed(entry));
+
 	if (inode) {
 		security_d_instantiate(entry, inode);
 		spin_lock(&inode->i_lock);
@@ -2986,8 +2989,6 @@ struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry)
 	if (IS_ERR(inode))
 		return ERR_CAST(inode);
 
-	BUG_ON(!d_unhashed(dentry));
-
 	if (!inode)
 		goto out;
 
-- 
2.1.0

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Thread

NFS/d_splice_alias breakage Oleg Drokin <green@linuxhacker.ru> - 2016-06-03 01:10 +0200
  [PATCH] Allow d_splice_alias to accept hashed dentries green@linuxhacker.ru - 2016-06-03 02:10 +0200
    Re: [PATCH] Allow d_splice_alias to accept hashed dentries Oleg Drokin <green@linuxhacker.ru> - 2016-06-03 02:30 +0200
  Re: NFS/d_splice_alias breakage Trond Myklebust <trondmy@primarydata.com> - 2016-06-03 02:50 +0200
    Re: NFS/d_splice_alias breakage Oleg Drokin <green@linuxhacker.ru> - 2016-06-03 03:00 +0200
      Re: NFS/d_splice_alias breakage Al Viro <viro@ZenIV.linux.org.uk> - 2016-06-03 05:30 +0200
        Re: NFS/d_splice_alias breakage Al Viro <viro@ZenIV.linux.org.uk> - 2016-06-03 05:40 +0200
    Re: NFS/d_splice_alias breakage Al Viro <viro@ZenIV.linux.org.uk> - 2016-06-03 05:30 +0200
  Re: NFS/d_splice_alias breakage Al Viro <viro@ZenIV.linux.org.uk> - 2016-06-03 05:40 +0200
    Re: NFS/d_splice_alias breakage Oleg Drokin <green@linuxhacker.ru> - 2016-06-03 05:50 +0200
      Re: NFS/d_splice_alias breakage Al Viro <viro@ZenIV.linux.org.uk> - 2016-06-03 06:30 +0200
        Re: NFS/d_splice_alias breakage Al Viro <viro@ZenIV.linux.org.uk> - 2016-06-03 06:50 +0200
          Re: NFS/d_splice_alias breakage Al Viro <viro@ZenIV.linux.org.uk> - 2016-06-03 07:00 +0200
        Re: NFS/d_splice_alias breakage Oleg Drokin <green@linuxhacker.ru> - 2016-06-03 07:00 +0200
          Re: NFS/d_splice_alias breakage Al Viro <viro@ZenIV.linux.org.uk> - 2016-06-03 08:00 +0200
            Re: NFS/d_splice_alias breakage Oleg Drokin <green@linuxhacker.ru> - 2016-06-07 01:40 +0200
              Re: NFS/d_splice_alias breakage Oleg Drokin <green@linuxhacker.ru> - 2016-06-10 03:40 +0200
                Re: NFS/d_splice_alias breakage Oleg Drokin <green@linuxhacker.ru> - 2016-06-10 18:50 +0200
        Dcache oops Oleg Drokin <green@linuxhacker.ru> - 2016-06-03 18:40 +0200
          Re: Dcache oops Al Viro <viro@ZenIV.linux.org.uk> - 2016-06-03 20:30 +0200
            Re: Dcache oops Oleg Drokin <green@linuxhacker.ru> - 2016-06-03 20:40 +0200
              Re: Dcache oops Al Viro <viro@ZenIV.linux.org.uk> - 2016-06-03 22:10 +0200
                Re: Dcache oops Linus Torvalds <torvalds@linux-foundation.org> - 2016-06-03 23:20 +0200
                Re: Dcache oops Al Viro <viro@ZenIV.linux.org.uk> - 2016-06-03 23:30 +0200
                Re: Dcache oops Linus Torvalds <torvalds@linux-foundation.org> - 2016-06-04 00:10 +0200
                Re: Dcache oops Al Viro <viro@ZenIV.linux.org.uk> - 2016-06-04 00:30 +0200
                Re: Dcache oops Al Viro <viro@ZenIV.linux.org.uk> - 2016-06-04 00:30 +0200
                Re: Dcache oops Al Viro <viro@ZenIV.linux.org.uk> - 2016-06-04 00:40 +0200
                Re: Dcache oops Oleg Drokin <green@linuxhacker.ru> - 2016-06-04 00:50 +0200
                Re: Dcache oops Oleg Drokin <green@linuxhacker.ru> - 2016-06-04 02:00 +0200
                Re: Dcache oops Al Viro <viro@ZenIV.linux.org.uk> - 2016-06-04 03:00 +0200
                Re: Dcache oops Jeff Layton <jlayton@poochiereds.net> - 2016-06-04 14:30 +0200
                Re: Dcache oops Oleg Drokin <green@linuxhacker.ru> - 2016-06-04 18:20 +0200
                [PATCH] nfs4: Fix potential use after free of state in nfs4_do_reclaim. green@linuxhacker.ru - 2016-06-04 18:30 +0200
                Re: [PATCH] nfs4: Fix potential use after free of state in  nfs4_do_reclaim. Jeff Layton <jlayton@poochiereds.net> - 2016-06-04 22:00 +0200
                Re: Dcache oops Linus Torvalds <torvalds@linux-foundation.org> - 2016-06-04 00:40 +0200
                Re: Dcache oops Oleg Drokin <green@linuxhacker.ru> - 2016-06-04 00:50 +0200
                Re: Dcache oops Al Viro <viro@ZenIV.linux.org.uk> - 2016-06-04 00:50 +0200
                Re: Dcache oops Oleg Drokin <green@linuxhacker.ru> - 2016-06-03 23:20 +0200
                Re: Dcache oops Al Viro <viro@ZenIV.linux.org.uk> - 2016-06-03 23:50 +0200
                Re: Dcache oops Al Viro <viro@ZenIV.linux.org.uk> - 2016-06-04 00:20 +0200

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