Re: [PATCH][RESEND] vfs: Make __d_materialise_dentry() set the materialised dentry name correctly

["Yan, Zheng" <zheng.z.yan@intel.com>]

Hi Al,

Could you include this in 3.15

Regards
Yan, Zheng

On 03/06/2014 10:35 PM, Trond Myklebust wrote:
> 
> On Mar 6, 2014, at 9:16, Yan, Zheng <zheng.z.yan@intel.com> wrote:
> 
>> From: David Howells <dhowells@redhat.com>
>>
>> Make __d_materialise_dentry() set the materialised dentry name correctly by
>> flipping the arguments to switch_names().
>>
>> switch_names() is lazy: if both names are internal to their dentries, it'll
>> overwrite that of the first dentry with that of the second, and won't update
>> that of the second.
>>
>> In the case of __d_materialise_dentry(), the second is an already extant
>> anonymous dentry that we want to insert into the tree in place of the dentry we
>> just looked up[*].  However, the dentry we just looked up carries the name we
>> actually want to use.
>>
>> [*] This is used by NFS to join a mount of a subtree into a mount of a tree
>> nearer the root when the two meet, where both mounts share a superblock and
>> thus a set of dentries.
>>
>> Signed-off-by: David Howells <dhowells@redhat.com>
>> ---
>> fs/dcache.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/fs/dcache.c b/fs/dcache.c
>> index 265e0ce..ff779d4 100644
>> --- a/fs/dcache.c
>> +++ b/fs/dcache.c
>> @@ -2698,7 +2698,7 @@ static void __d_materialise_dentry(struct dentry *dentry, struct dentry *anon)
>>
>> 	dparent = dentry->d_parent;
>>
>> -	switch_names(dentry, anon);
>> +	switch_names(anon, dentry);
>> 	swap(dentry->d_name.hash, anon->d_name.hash);
>>
>> 	dentry->d_parent = dentry;
> 
> Well spotted...
> 
> We ought to better document the fact that ’switch_names’ is asymmetrical. Perhaps change it to ‘update_target_name’, and then switch the argument names so that the ’target’ really is the thing that gets updated?
> 
> _________________________________
> Trond Myklebust
> Linux NFS client maintainer, PrimaryData
> trond.myklebust@primarydata.com
> 

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