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List:       ceph-devel
Subject:    Re: [PATCH] ceph: reset i_requested_max_size if file write is not wanted
From:       Jeff Layton <jlayton () kernel ! org>
Date:       2020-03-30 18:28:37
Message-ID: 9f75e21301149a550ab6868cf645a89b538f16d0.camel () kernel ! org
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On Mon, 2020-03-30 at 22:26 +0800, Yan, Zheng wrote:
> On 3/30/20 10:00 PM, Jeff Layton wrote:
> > On Mon, 2020-03-30 at 19:56 +0800, Yan, Zheng wrote:
> > > write can stuck at waiting for larger max_size in following sequence of
> > > events:
> > > 
> > > - client opens a file and writes to position 'A' (larger than unit of
> > >    max size increment)
> > > - client closes the file handle and updates wanted caps (not wanting
> > >    file write caps)
> > > - client opens and truncates the file, writes to position 'A' again.
> > > 
> > > At the 1st event, client set inode's requested_max_size to 'A'. At the
> > > 2nd event, mds removes client's writable range, but client does not reset
> > > requested_max_size. At the 3rd event, client does not request max size
> > > because requested_max_size is already larger than 'A'.
> > > 
> > > Signed-off-by: "Yan, Zheng" <zyan@redhat.com>
> > > ---
> > >   fs/ceph/caps.c | 29 +++++++++++++++++++----------
> > >   1 file changed, 19 insertions(+), 10 deletions(-)
> > > 
> > > diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c
> > > index f8b51d0c8184..61808793e0c0 100644
> > > --- a/fs/ceph/caps.c
> > > +++ b/fs/ceph/caps.c
> > > @@ -1363,8 +1363,12 @@ static void __prep_cap(struct cap_msg_args *arg, struct ceph_cap *cap,
> > >   	arg->size = inode->i_size;
> > >   	ci->i_reported_size = arg->size;
> > >   	arg->max_size = ci->i_wanted_max_size;
> > > -	if (cap == ci->i_auth_cap)
> > > -		ci->i_requested_max_size = arg->max_size;
> > > +	if (cap == ci->i_auth_cap) {
> > > +		if (want & CEPH_CAP_ANY_FILE_WR)
> > > +			ci->i_requested_max_size = arg->max_size;
> > > +		else
> > > +			ci->i_requested_max_size = 0;
> > > +	}
> > >   
> > >   	if (flushing & CEPH_CAP_XATTR_EXCL) {
> > >   		arg->old_xattr_buf = __ceph_build_xattrs_blob(ci);
> > > @@ -3343,10 +3347,6 @@ static void handle_cap_grant(struct inode *inode,
> > >   				ci->i_requested_max_size = 0;
> > >   			}
> > >   			wake = true;
> > > -		} else if (ci->i_wanted_max_size > ci->i_max_size &&
> > > -			   ci->i_wanted_max_size > ci->i_requested_max_size) {
> > > -			/* CEPH_CAP_OP_IMPORT */
> > > -			wake = true;
> > >   		}
> > >   	}
> > >   
> > > @@ -3422,9 +3422,18 @@ static void handle_cap_grant(struct inode *inode,
> > >   			fill_inline = true;
> > >   	}
> > >   
> > > -	if (le32_to_cpu(grant->op) == CEPH_CAP_OP_IMPORT) {
> > > +	if (ci->i_auth_cap == cap &&
> > > +	    le32_to_cpu(grant->op) == CEPH_CAP_OP_IMPORT) {
> > >   		if (newcaps & ~extra_info->issued)
> > >   			wake = true;
> > > +
> > > +		if (ci->i_requested_max_size > max_size ||
> > > +		    !(le32_to_cpu(grant->wanted) & CEPH_CAP_ANY_FILE_WR)) {
> > > +			/* re-request max_size if necessary */
> > > +			ci->i_requested_max_size = 0;
> > > +			wake = true;
> > > +		}
> > > +
> > >   		ceph_kick_flushing_inode_caps(session, ci);
> > >   		spin_unlock(&ci->i_ceph_lock);
> > >   		up_read(&session->s_mdsc->snap_rwsem);
> > > @@ -3882,9 +3891,6 @@ static void handle_cap_import(struct ceph_mds_client *mdsc,
> > >   		__ceph_remove_cap(ocap, (ph->flags & CEPH_CAP_FLAG_RELEASE));
> > >   	}
> > >   
> > > -	/* make sure we re-request max_size, if necessary */
> > > -	ci->i_requested_max_size = 0;
> > > -
> > >   	*old_issued = issued;
> > >   	*target_cap = cap;
> > >   }
> > > @@ -4318,6 +4324,9 @@ int ceph_encode_inode_release(void **p, struct inode *inode,
> > >   				cap->issued &= ~drop;
> > >   				cap->implemented &= ~drop;
> > >   				cap->mds_wanted = wanted;
> > > +				if (cap == ci->i_auth_cap &&
> > > +				    !(wanted & CEPH_CAP_ANY_FILE_WR))
> > > +					ci->i_requested_max_size = 0;
> > >   			} else {
> > >   				dout("encode_inode_release %p cap %p %s"
> > >   				     " (force)\n", inode, cap,
> > 
> > Thanks Zheng. I assume this is a regression in the "don't request caps
> > for idle open files" series? If so, is there a commit that definitively
> > broke it? It'd be good to add a Fixes: tag for that if we can to help
> > backporters.
> > 
> > Thanks,
> > 
> 
> It's not regression. It' kclient version of 
> https://tracker.ceph.com/issues/44801. I only saw this bug in ceph-fuse, 
> kclient contain this bug in theory.
> 

Got it, thanks. Merged into ceph-client/testing. I did not mark it for
stable. Let me know if you think it should be.

Cheers,
-- 
Jeff Layton <jlayton@kernel.org>

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