Re: [PATCH 1/4] fs/notify: fdinfo can report unsupported file handles.

[NeilBrown]

On Mon, Dec 11 2017, Al Viro wrote:

> On Mon, Dec 11, 2017 at 05:04:05PM +1100, NeilBrown wrote:
>> @@ -385,7 +385,9 @@ int exportfs_encode_inode_fh(struct inode *inode, struct 
>> fid *fid,
>>  {
>>      const struct export_operations *nop = inode->i_sb->s_export_op;
>>  
>> -    if (nop && nop->encode_fh)
>> +    if (nop)
>> +            return FILEID_INVALID;
>> +    if (nop->encode_fh)
>>              return nop->encode_fh(inode, fid->raw, max_len, parent);
>
> This might as well have been
>
>       if (nop)
>               return FILEID_INVALID;
>       BUG();
>
> Have you ever tested that?

I have now - except for testing against Amazon EFS.
Only problem is the one you found - thanks.

NeilBrown

-----------8<------------>8----------------
From: NeilBrown <ne...@suse.com>
Date: Mon, 11 Dec 2017 16:41:01 +1100
Subject: [PATCH] fs/notify: fdinfo can report unsupported file handles.

If a filesystem does not set sb->s_export_op, then it
does not support filehandles and export_fs_encode_fh()
and exportfs_encode_inode_fh() should not be called.
They will use export_encode_fh() is which is a default
that uses inode number generation number, but in general
they may not be stable.

So change exportfs_encode_inode_fh() to return FILEID_INVALID
if called on an unsupported Filesystem.  Currently only
notify/fdinfo can do that.

Also remove the WARNing from fdinfo when exportfs_encode_inode_fh()
returns FILEID_INVALID, as that is no an erroneous condition.

Signed-off-by: NeilBrown <ne...@suse.com>
---
 fs/exportfs/expfs.c | 4 +++-
 fs/notify/fdinfo.c  | 4 +---
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/fs/exportfs/expfs.c b/fs/exportfs/expfs.c
index 329a5d103846..2fff333b750c 100644
--- a/fs/exportfs/expfs.c
+++ b/fs/exportfs/expfs.c
@@ -385,7 +385,9 @@ int exportfs_encode_inode_fh(struct inode *inode, struct 
fid *fid,
 {
        const struct export_operations *nop = inode->i_sb->s_export_op;
 
-       if (nop && nop->encode_fh)
+       if (!nop)
+               return FILEID_INVALID;
+       if (nop->encode_fh)
                return nop->encode_fh(inode, fid->raw, max_len, parent);
 
        return export_encode_fh(inode, fid, max_len, parent);
diff --git a/fs/notify/fdinfo.c b/fs/notify/fdinfo.c
index d478629c728b..d1135ed61229 100644
--- a/fs/notify/fdinfo.c
+++ b/fs/notify/fdinfo.c
@@ -50,10 +50,8 @@ static void show_mark_fhandle(struct seq_file *m, struct 
inode *inode)
        size = f.handle.handle_bytes >> 2;
 
        ret = exportfs_encode_inode_fh(inode, (struct fid *)f.handle.f_handle, 
&size, 0);
-       if ((ret == FILEID_INVALID) || (ret < 0)) {
-               WARN_ONCE(1, "Can't encode file handler for inotify: %d\n", 
ret);
+       if ((ret == FILEID_INVALID) || (ret < 0))
                return;
-       }
 
        f.handle.handle_type = ret;
        f.handle.handle_bytes = size * sizeof(u32);
-- 
2.14.0.rc0.dirty

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