Patch "NFSD: Make nfsd4_setattr() wait before returning NFS4ERR_DELAY" has been added to the 5.10-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    NFSD: Make nfsd4_setattr() wait before returning NFS4ERR_DELAY

to the 5.10-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     nfsd-make-nfsd4_setattr-wait-before-returning-nfs4er.patch
and it can be found in the queue-5.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 8576b08945891abc687a49a8f1fb6729c2670baf
Author: Chuck Lever <chuck.lever@xxxxxxxxxx>
Date:   Thu Sep 8 18:14:13 2022 -0400

    NFSD: Make nfsd4_setattr() wait before returning NFS4ERR_DELAY
    
    [ Upstream commit 34b91dda7124fc3259e4b2ae53e0c933dedfec01 ]
    
    nfsd_setattr() can kick off a CB_RECALL (via
    notify_change() -> break_lease()) if a delegation is present. Before
    returning NFS4ERR_DELAY, give the client holding that delegation a
    chance to return it and then retry the nfsd_setattr() again, once.
    
    Link: https://bugzilla.linux-nfs.org/show_bug.cgi?id=354
    Tested-by: Igor Mammedov <imammedo@xxxxxxxxxx>
    Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
    Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx>
    Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index e32b0c807ea9d..dc79db261d6a2 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -426,6 +426,7 @@ nfsd_setattr(struct svc_rqst *rqstp, struct svc_fh *fhp,
 	int		host_err;
 	bool		get_write_count;
 	bool		size_change = (iap->ia_valid & ATTR_SIZE);
+	int		retries;
 
 	if (iap->ia_valid & ATTR_SIZE) {
 		accmode |= NFSD_MAY_WRITE|NFSD_MAY_OWNER_OVERRIDE;
@@ -480,7 +481,13 @@ nfsd_setattr(struct svc_rqst *rqstp, struct svc_fh *fhp,
 	}
 
 	inode_lock(inode);
-	host_err = __nfsd_setattr(dentry, iap);
+	for (retries = 1;;) {
+		host_err = __nfsd_setattr(dentry, iap);
+		if (host_err != -EAGAIN || !retries--)
+			break;
+		if (!nfsd_wait_for_delegreturn(rqstp, inode))
+			break;
+	}
 	if (attr->na_seclabel && attr->na_seclabel->len)
 		attr->na_labelerr = security_inode_setsecctx(dentry,
 			attr->na_seclabel->data, attr->na_seclabel->len);