>> From: Miklos Szeredi <mszeredi@xxxxxxxxxx>
>>
>> This series fixes bugs in nfs and ext4 due to 4bacc9c9234c ("overlayfs: Make
>> f_path always point to the overlay and f_inode to the underlay").
>>
>> Regular files opened on overlayfs will result in the file being opened on
>> the underlying filesystem, while f_path points to the overlayfs
>> mount/dentry.
>>
>> This confuses filesystems which get the dentry from struct file and assume
>> it's theirs.
>>
>> Add a new helper, file_dentry() [*], to get the filesystem's own dentry
>> from the file. This simply compares file_inode(file->f_path.dentry) to
>> file_inode(file) and if they are equal returns file->f_path.dentry (this is
>> the common, non-overlayfs case).
>>
>> In the uncommon case (regular file on overlayfs) it will call into
>> overlayfs's ->d_native_dentry() to get the underlying dentry matching
>> file_inode(file).
>>
>> [*] If possible, it's better simply to use file_inode() instead.
Hopefully this is not so late as to be useless!
For this entire series:
Tested-by: Daniel Axtens <dja@xxxxxxxxxx>
Regards,
Daniel
>>
>> Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxxxxx>
>> Tested-by: Goldwyn Rodrigues <rgoldwyn@xxxxxxxx>
>> Reviewed-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
>> Cc: <stable@xxxxxxxxxxxxxxx> # v4.2
>> Cc: David Howells <dhowells@xxxxxxxxxx>
>> Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
>> Cc: Theodore Ts'o <tytso@xxxxxxx>
>> Cc: Daniel Axtens <dja@xxxxxxxxxx>
>> ---
>> fs/open.c | 11 +++++++++++
>> fs/overlayfs/super.c | 16 ++++++++++++++++
>> include/linux/dcache.h | 1 +
>> include/linux/fs.h | 2 ++
>> 4 files changed, 30 insertions(+)
>
> I have this patch in the ext4.git tree, but I'd like to get an
> Acked-by from Al before I send a pull request to Linus.
>
> Al? Any objections to my sending in this change via the ext4 tree?
>
> - Ted
>
>>
>> diff --git a/fs/open.c b/fs/open.c
>> index 55bdc75e2172..6326c11eda78 100644
>> --- a/fs/open.c
>> +++ b/fs/open.c
>> @@ -831,6 +831,17 @@ char *file_path(struct file *filp, char *buf, int buflen)
>> }
>> EXPORT_SYMBOL(file_path);
>>
>> +struct dentry *file_dentry(const struct file *file)
>> +{
>> + struct dentry *dentry = file->f_path.dentry;
>> +
>> + if (likely(d_inode(dentry) == file_inode(file)))
>> + return dentry;
>> + else
>> + return dentry->d_op->d_native_dentry(dentry, file_inode(file));
>> +}
>> +EXPORT_SYMBOL(file_dentry);
>> +
>> /**
>> * vfs_open - open the file at the given path
>> * @path: path to open
>> diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
>> index 619ad4b016d2..5142aa2034c4 100644
>> --- a/fs/overlayfs/super.c
>> +++ b/fs/overlayfs/super.c
>> @@ -336,14 +336,30 @@ static int ovl_dentry_weak_revalidate(struct dentry *dentry, unsigned int flags)
>> return ret;
>> }
>>
>> +static struct dentry *ovl_d_native_dentry(struct dentry *dentry,
>> + struct inode *inode)
>> +{
>> + struct ovl_entry *oe = dentry->d_fsdata;
>> + struct dentry *realentry = ovl_upperdentry_dereference(oe);
>> +
>> + if (realentry && inode == d_inode(realentry))
>> + return realentry;
>> + realentry = __ovl_dentry_lower(oe);
>> + if (realentry && inode == d_inode(realentry))
>> + return realentry;
>> + BUG();
>> +}
>> +
>> static const struct dentry_operations ovl_dentry_operations = {
>> .d_release = ovl_dentry_release,
>> .d_select_inode = ovl_d_select_inode,
>> + .d_native_dentry = ovl_d_native_dentry,
>> };
>>
>> static const struct dentry_operations ovl_reval_dentry_operations = {
>> .d_release = ovl_dentry_release,
>> .d_select_inode = ovl_d_select_inode,
>> + .d_native_dentry = ovl_d_native_dentry,
>> .d_revalidate = ovl_dentry_revalidate,
>> .d_weak_revalidate = ovl_dentry_weak_revalidate,
>> };
>> diff --git a/include/linux/dcache.h b/include/linux/dcache.h
>> index c4b5f4b3f8f8..99ecb6de636c 100644
>> --- a/include/linux/dcache.h
>> +++ b/include/linux/dcache.h
>> @@ -161,6 +161,7 @@ struct dentry_operations {
>> struct vfsmount *(*d_automount)(struct path *);
>> int (*d_manage)(struct dentry *, bool);
>> struct inode *(*d_select_inode)(struct dentry *, unsigned);
>> + struct dentry *(*d_native_dentry)(struct dentry *, struct inode *);
>> } ____cacheline_aligned;
>>
>> /*
>> diff --git a/include/linux/fs.h b/include/linux/fs.h
>> index ae681002100a..1091d9f43271 100644
>> --- a/include/linux/fs.h
>> +++ b/include/linux/fs.h
>> @@ -1234,6 +1234,8 @@ static inline struct inode *file_inode(const struct file *f)
>> return f->f_inode;
>> }
>>
>> +extern struct dentry *file_dentry(const struct file *file);
>> +
>> static inline int locks_lock_file_wait(struct file *filp, struct file_lock *fl)
>> {
>> return locks_lock_inode_wait(file_inode(filp), fl);
>> --
>> 2.1.4
>>
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