linux-kernel - [PATCH] fs/9p/xattr.c: catch the error of p9_client

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Date:   Wed, 25 Jul 2018 11:13:16 +0800
From:   piaojun <piaojun@...wei.com>
To:     Dominique Martinet <asmadeus@...ewreck.org>
CC:     "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "Eric Van Hensbergen" <ericvh@...il.com>,
        Ron Minnich <rminnich@...dia.gov>,
        "Latchesar Ionkov" <lucho@...kov.net>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        <v9fs-developer@...ts.sourceforge.net>, <groug@...d.org>
Subject: [PATCH] fs/9p/xattr.c: catch the error of p9_client_clunk when
 setting xattr failed

In my testing, v9fs_fid_xattr_set will return successfully even if the
backend ext4 filesystem has no space to store xattr key-value. That will
cause inconsistent behavior between front end and back end. The reason is
that lsetxattr will be triggered by p9_client_clunk, and unfortunately we
did not catch the error. This patch will catch the error to notify upper
caller.

p9_client_clunk (in 9p)
  p9_client_rpc(clnt, P9_TCLUNK, "d", fid->fid);
    v9fs_clunk (in qemu)
      put_fid
        free_fid
          v9fs_xattr_fid_clunk
            v9fs_co_lsetxattr
              s->ops->lsetxattr
                ext4_xattr_user_set (in host ext4 filesystem)

Signed-off-by: Jun Piao <piaojun@...wei.com>
---
 fs/9p/xattr.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/fs/9p/xattr.c b/fs/9p/xattr.c
index f329eee..352abc3 100644
--- a/fs/9p/xattr.c
+++ b/fs/9p/xattr.c
@@ -105,7 +105,7 @@ int v9fs_fid_xattr_set(struct p9_fid *fid, const char *name,
 {
 	struct kvec kvec = {.iov_base = (void *)value, .iov_len = value_len};
 	struct iov_iter from;
-	int retval;
+	int retval, err;

 	iov_iter_kvec(&from, WRITE | ITER_KVEC, &kvec, 1, value_len);

@@ -126,7 +126,9 @@ int v9fs_fid_xattr_set(struct p9_fid *fid, const char *name,
 			 retval);
 	else
 		p9_client_write(fid, 0, &from, &retval);
-	p9_client_clunk(fid);
+	err = p9_client_clunk(fid);
+	if (!retval && err)
+		retval = err;
 	return retval;
 }

--