On Oct 15, 2020, at 9:59 AM, Trond Myklebust trondmy@hammerspace.com wrote:
On Thu, 2020-10-15 at 09:36 -0400, Chuck Lever wrote:
On Oct 15, 2020, at 8:06 AM, Trond Myklebust < trondmy@hammerspace.com> wrote:
On Thu, 2020-10-15 at 00:39 +0530, Ashish Sangwan wrote:
On Wed, Oct 14, 2020 at 11:47 PM Trond Myklebust trondmy@hammerspace.com wrote:
On Tue, 2020-10-06 at 08:14 -0700, Ashish Sangwan wrote:
Request for mode bits and nlink count in the nfs4_get_referral call and if server returns them use them instead of hard coded values.
CC: stable@vger.kernel.org Signed-off-by: Ashish Sangwan ashishsangwan2@gmail.com
fs/nfs/nfs4proc.c | 20 +++++++++++++++++--- 1 file changed, 17 insertions(+), 3 deletions(-)
diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c index 6e95c85fe395..efec05c5f535 100644 --- a/fs/nfs/nfs4proc.c +++ b/fs/nfs/nfs4proc.c @@ -266,7 +266,9 @@ const u32 nfs4_fs_locations_bitmap[3] = { | FATTR4_WORD0_FSID | FATTR4_WORD0_FILEID | FATTR4_WORD0_FS_LOCATIONS,
FATTR4_WORD1_OWNER
FATTR4_WORD1_MODE| FATTR4_WORD1_NUMLINKS| FATTR4_WORD1_OWNER@@ -7594,16 +7596,28 @@ nfs4_listxattr_nfs4_user(struct inode *inode, char *list, size_t list_len) */ static void nfs_fixup_referral_attributes(struct nfs_fattr *fattr) {
bool fix_mode = true, fix_nlink = true;- if (!(((fattr->valid & NFS_ATTR_FATTR_MOUNTED_ON_FILEID)
|| (fattr->valid & NFS_ATTR_FATTR_FILEID)) && (fattr->valid & NFS_ATTR_FATTR_FSID) && (fattr->valid & NFS_ATTR_FATTR_V4_LOCATIONS))) return;
if (fattr->valid & NFS_ATTR_FATTR_MODE)fix_mode = false;if (fattr->valid & NFS_ATTR_FATTR_NLINK)fix_nlink = false;NFS_ATTR_FATTR_MODE | NFS_ATTR_FATTR_NLINK | NFS_ATTR_FATTR_V4_REFERRAL;
fattr->mode = S_IFDIR | S_IRUGO | S_IXUGO;fattr->nlink = 2;
if (fix_mode)fattr->mode = S_IFDIR | S_IRUGO | S_IXUGO;elsefattr->mode |= S_IFDIR;if (fix_nlink)fattr->nlink = 2;}
static int _nfs4_proc_fs_locations(struct rpc_clnt *client, struct inode *dir,
NACK to this patch. The whole point is that if the server has a referral, then it is not going to give us any attributes other than the ones we're already asking for because it may not even have a real directory. The client is required to fake up an inode, hence the existing code.
Hi Trond, thanks for reviewing the patch! Sorry but I didn't understand the reason to NACK it. Could you please elaborate your concern? These are the current attributes we request from the server on a referral: FATTR4_WORD0_CHANGE
FATTR4_WORD0_SIZE FATTR4_WORD0_FSID FATTR4_WORD0_FILEID FATTR4_WORD0_FS_LOCATIONS,
FATTR4_WORD1_OWNER
FATTR4_WORD1_OWNER_GROUP FATTR4_WORD1_RAWDEV FATTR4_WORD1_SPACE_USED FATTR4_WORD1_TIME_ACCESS FATTR4_WORD1_TIME_METADATA FATTR4_WORD1_TIME_MODIFY FATTR4_WORD1_MOUNTED_ON_FILEID,
So you are suggesting that it's ok to ask for SIZE, OWNER, OWNER GROUP, SPACE USED, TIMESTAMPs etc but not ok to ask for mode bits and numlinks?
No. We shouldn't be asking for any of that information for a referral because the server isn't supposed to return any values for it.
Chuck and Anna, what's the deal with commit c05cefcc7241? That appears to have changed the original code to speculatively assume that the server will violate RFC5661 Section 11.3.1 and/or RFC7530 Section 8.3.1.
The commit is an attempt to address the many complaints we've had about the ugly appearance of referral anchors. The strange "special" default values made the client appear to be broken, and was confusing to some. I consider this to be a UX issue: the information displayed in this case is not meant to be factual, but rather to prevent the user concluding that something is wrong.
I'm not attached to this particular solution, though. Does it make sense to perform the referral mount before returning "ls" results so that the target server has a chance to supply reasonable attribute values for the mounted-on directory object? Just spit balling here.
Specifically, the paragraph that says:
" Other attributes SHOULD NOT be made available for absent file systems, even when it is possible to provide them. The server should not assume that more information is always better and should avoid gratuitously providing additional information."
So why is the client asking for them?
This paragraph (and it's most modern incarnation in RFC 8881 Section 11.4.1) describes server behavior. The current client behavior is spec-compliant because there is no explicit prohibition in the spec language against a client requesting additional attributes in this case.
Either the server can clear those bitmap flags on the GETATTR reply and not supply those attributes, and clients must be prepared for that.
Or, it's also possible to read this paragraph to mean that the server can provide those attributes and the values should not reflect attributes for the absent file system, but rather something else (eg, server-manufactured defaults, or the attributes from the object on the source server).
And since this is a SHOULD NOT rather than a MUST NOT, servers are still free to return information about the absent file system. Clients are not guaranteed this will be the case, however.
I don't think c05cefcc7241 makes any assumption about whether the server is lying about the extra attributes. Perhaps the server has no better values for these attributes than the client's defaults were.
SHOULD / SHOULD NOT indicates actions that the server is required to take in the absence of a very good reason to do otherwise. In other words, the client should expect the majority of servers to behave in a certain manner.
It doesn't matter that the client's behaviour is spec compliant. We're asking for information that is not supposed to be divulged by the majority of servers, Furthermore, that information is, quite frankly, utterly irrelevant to the client and application running on it. Any attempt to access that fake object will result in a submount of something completely different on top of that object.
IOW: the only difference here is you're asking that the server provide us with a faked up object (which it is not supposed to do), whereas previously, we were faking that object up ourselves. What's the big deal here?
Right, that boils it down nicely.
The difference has been that by and large the server-provided values don't look broken to users. Perhaps all we need to do is select better defaults for these attributes on Linux clients. I haven't followed Ashish's requirements, so I can't speak to them.
Here is some history.
https://lore.kernel.org/linux-nfs/CAD8zhTAAvTKhp6k0vYRMnhZW5pxjstpBiDKLgoXoc...
-- Chuck Lever