Re: [PATCH 3/3] nfs: Store and use inode in nfs_open_context

[Goldwyn Rodrigues <rgoldwyn@suse.de>]

On 03/04/2016 07:41 AM, Trond Myklebust wrote:
> On Fri, Mar 4, 2016 at 5:17 AM, Miklos Szeredi <miklos@szeredi.hu> wrote:
>> On Thu, Mar 03, 2016 at 09:16:33AM +0100, Miklos Szeredi wrote:
>>> My plan was to introduce a file_dentry() helper that MUST be used by
>>> filesystems to get the dentry from the file and that makes sure it's
>>> the right one (check against file_inode()).   If not, then we could
>>> call into overlayfs to return the right one, similar to
>>> ->d_select_inode(), except we want to have a dentry and we want to
>>> have *a particular dentry* matching file_inode() (the file could have
>>> been copied up in the mean time).
>>
>> Something like the following (untested, against overlayfs-next.git)
>>
>> Thanks,
>> Miklos
>>
>> ---
>>   fs/nfs/dir.c           |    6 +++---
>>   fs/nfs/inode.c         |    2 +-
>>   fs/nfs/nfs4file.c      |    4 ++--
>>   fs/open.c              |   11 +++++++++++
>>   fs/overlayfs/super.c   |   16 ++++++++++++++++
>>   include/linux/dcache.h |    1 +
>>   include/linux/fs.h     |    2 ++
>>   7 files changed, 36 insertions(+), 6 deletions(-)
>>
>> --- a/fs/nfs/dir.c
>> +++ b/fs/nfs/dir.c
>> @@ -377,7 +377,7 @@ int nfs_readdir_xdr_filler(struct page *
>>    again:
>>          timestamp = jiffies;
>>          gencount = nfs_inc_attr_generation_counter();
>> -       error = NFS_PROTO(inode)->readdir(file->f_path.dentry, cred, entry->cookie, pages,
>> +       error = NFS_PROTO(inode)->readdir(file_dentry(file), cred, entry->cookie, pages,
>>                                            NFS_SERVER(inode)->dtsize, desc->plus);
>>          if (error < 0) {
>>                  /* We requested READDIRPLUS, but the server doesn't grok it */
>> @@ -560,7 +560,7 @@ int nfs_readdir_page_filler(nfs_readdir_
>>                  count++;
>>
>>                  if (desc->plus != 0)
>> -                       nfs_prime_dcache(desc->file->f_path.dentry, entry);
>> +                       nfs_prime_dcache(file_dentry(desc->file), entry);
>>
>>                  status = nfs_readdir_add_to_array(entry, page);
>>                  if (status != 0)
>> @@ -864,7 +864,7 @@ static bool nfs_dir_mapping_need_revalid
>>    */
>>   static int nfs_readdir(struct file *file, struct dir_context *ctx)
>>   {
>> -       struct dentry   *dentry = file->f_path.dentry;
>> +       struct dentry   *dentry = file_dentry(file);
>>          struct inode    *inode = d_inode(dentry);
>>          nfs_readdir_descriptor_t my_desc,
>>                          *desc = &my_desc;
>> --- a/fs/nfs/inode.c
>> +++ b/fs/nfs/inode.c
>> @@ -940,7 +940,7 @@ int nfs_open(struct inode *inode, struct
>>   {
>>          struct nfs_open_context *ctx;
>>
>> -       ctx = alloc_nfs_open_context(filp->f_path.dentry, filp->f_mode);
>> +       ctx = alloc_nfs_open_context(file_dentry(filp), filp->f_mode);
>>          if (IS_ERR(ctx))
>>                  return PTR_ERR(ctx);
>>          nfs_file_set_open_context(filp, ctx);
>> --- a/fs/nfs/nfs4file.c
>> +++ b/fs/nfs/nfs4file.c
>> @@ -26,7 +26,7 @@ static int
>>   nfs4_file_open(struct inode *inode, struct file *filp)
>>   {
>>          struct nfs_open_context *ctx;
>> -       struct dentry *dentry = filp->f_path.dentry;
>> +       struct dentry *dentry = file_dentry(filp);
>>          struct dentry *parent = NULL;
>>          struct inode *dir;
>>          unsigned openflags = filp->f_flags;
>> @@ -57,7 +57,7 @@ nfs4_file_open(struct inode *inode, stru
>>          parent = dget_parent(dentry);
>>          dir = d_inode(parent);
>>
>> -       ctx = alloc_nfs_open_context(filp->f_path.dentry, filp->f_mode);
>> +       ctx = alloc_nfs_open_context(file_dentry(filp), filp->f_mode);
>>          err = PTR_ERR(ctx);
>>          if (IS_ERR(ctx))
>>                  goto out;
>> --- a/include/linux/fs.h
>> +++ b/include/linux/fs.h
>> @@ -1234,6 +1234,8 @@ static inline struct inode *file_inode(c
>>          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);
>> --- a/fs/open.c
>> +++ b/fs/open.c
>> @@ -831,6 +831,17 @@ char *file_path(struct file *filp, char
>>   }
>>   EXPORT_SYMBOL(file_path);
>>
>> +struct dentry *file_dentry(const struct file *file)
>> +{
>> +       struct dentry *dentry = file->f_path.dentry;
>> +
>> +       if (d_inode(dentry) == file_inode(file))
>> +               return dentry;
>> +       else
>> +               return dentry->d_op->d_select_dentry(dentry, file_inode(file));
>> +}
>> +EXPORT_SYMBOL(file_dentry);
>> +
>>   /**
>>    * vfs_open - open the file at the given path
>>    * @path: path to open
>> --- a/fs/overlayfs/super.c
>> +++ b/fs/overlayfs/super.c
>> @@ -336,14 +336,30 @@ static int ovl_dentry_weak_revalidate(st
>>          return ret;
>>   }
>>
>> +static struct dentry *ovl_d_select_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_select_dentry = ovl_d_select_dentry,
>>   };
>>
>>   static const struct dentry_operations ovl_reval_dentry_operations = {
>>          .d_release = ovl_dentry_release,
>>          .d_select_inode = ovl_d_select_inode,
>> +       .d_select_dentry = ovl_d_select_dentry,
>>          .d_revalidate = ovl_dentry_revalidate,
>>          .d_weak_revalidate = ovl_dentry_weak_revalidate,
>>   };
>> --- 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_select_dentry)(struct dentry *, struct inode *);
>>   } ____cacheline_aligned;
>>
>>   /*
>
> Thanks Miklos! That looks reasonable, assuming it tests out correctly.
>

Tested and it looks good. Thanks Miklos.

Tested-by: Goldwyn Rodrigues <rgoldwyn@suse.com>


-- 
Goldwyn