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Subject[PATCH 6/8] afs: Fix a Sparse warning in xdr_decode_AFSFetchStatus()
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Sparse doesn't appear able to handle the conditionally-taken locks in
xdr_decode_AFSFetchStatus(), even though the lock and unlock are both
contingent on the same unvarying function argument.

Deal with this by interpolating a wrapper function that takes the lock if
needed and calls xdr_decode_AFSFetchStatus() on two separate branches, one
with the lock held and one without.

This allows Sparse to work out the locking.

Signed-off-by: David Howells <dhowells@redhat.com>
---

fs/afs/fsclient.c | 97 ++++++++++++++++++++++++++++++-----------------------
1 file changed, 55 insertions(+), 42 deletions(-)

diff --git a/fs/afs/fsclient.c b/fs/afs/fsclient.c
index efacdb7c1dee..b695d9e16c65 100644
--- a/fs/afs/fsclient.c
+++ b/fs/afs/fsclient.c
@@ -137,10 +137,6 @@ static int xdr_decode_AFSFetchStatus(struct afs_call *call,
u64 data_version, size;
u32 type, abort_code;
u8 flags = 0;
- int ret;
-
- if (vnode)
- write_seqlock(&vnode->cb_lock);

if (xdr->if_version != htonl(AFS_FSTATUS_VERSION)) {
pr_warn("Unknown AFSFetchStatus version %u\n", ntohl(xdr->if_version));
@@ -168,8 +164,7 @@ static int xdr_decode_AFSFetchStatus(struct afs_call *call,
case AFS_FTYPE_INVALID:
if (abort_code != 0) {
status->abort_code = abort_code;
- ret = 0;
- goto out;
+ return 0;
}
/* Fall through */
default:
@@ -222,17 +217,35 @@ static int xdr_decode_AFSFetchStatus(struct afs_call *call,
flags);
}

- ret = 0;
-
-out:
- if (vnode)
- write_sequnlock(&vnode->cb_lock);
- return ret;
+ return 0;

bad:
xdr_dump_bad(*_bp);
- ret = afs_protocol_error(call, -EBADMSG);
- goto out;
+ return afs_protocol_error(call, -EBADMSG);
+}
+
+/*
+ * Decode the file status. We need to lock the target vnode if we're going to
+ * update its status so that stat() sees the attributes update atomically.
+ */
+static int afs_decode_status(struct afs_call *call,
+ const __be32 **_bp,
+ struct afs_file_status *status,
+ struct afs_vnode *vnode,
+ const afs_dataversion_t *expected_version,
+ struct afs_read *read_req)
+{
+ int ret;
+
+ if (!vnode)
+ return xdr_decode_AFSFetchStatus(call, _bp, status, vnode,
+ expected_version, read_req);
+
+ write_seqlock(&vnode->cb_lock);
+ ret = xdr_decode_AFSFetchStatus(call, _bp, status, vnode,
+ expected_version, read_req);
+ write_sequnlock(&vnode->cb_lock);
+ return ret;
}

/*
@@ -374,8 +387,8 @@ static int afs_deliver_fs_fetch_status_vnode(struct afs_call *call)

/* unmarshall the reply once we've received all of it */
bp = call->buffer;
- if (xdr_decode_AFSFetchStatus(call, &bp, &vnode->status, vnode,
- &call->expected_version, NULL) < 0)
+ if (afs_decode_status(call, &bp, &vnode->status, vnode,
+ &call->expected_version, NULL) < 0)
return afs_protocol_error(call, -EBADMSG);
xdr_decode_AFSCallBack(call, vnode, &bp);
if (call->reply[1])
@@ -555,8 +568,8 @@ static int afs_deliver_fs_fetch_data(struct afs_call *call)
return ret;

bp = call->buffer;
- if (xdr_decode_AFSFetchStatus(call, &bp, &vnode->status, vnode,
- &vnode->status.data_version, req) < 0)
+ if (afs_decode_status(call, &bp, &vnode->status, vnode,
+ &vnode->status.data_version, req) < 0)
return afs_protocol_error(call, -EBADMSG);
xdr_decode_AFSCallBack(call, vnode, &bp);
if (call->reply[1])
@@ -708,9 +721,9 @@ static int afs_deliver_fs_create_vnode(struct afs_call *call)
/* unmarshall the reply once we've received all of it */
bp = call->buffer;
xdr_decode_AFSFid(&bp, call->reply[1]);
- if (xdr_decode_AFSFetchStatus(call, &bp, call->reply[2], NULL, NULL, NULL) < 0 ||
- xdr_decode_AFSFetchStatus(call, &bp, &vnode->status, vnode,
- &call->expected_version, NULL) < 0)
+ if (afs_decode_status(call, &bp, call->reply[2], NULL, NULL, NULL) < 0 ||
+ afs_decode_status(call, &bp, &vnode->status, vnode,
+ &call->expected_version, NULL) < 0)
return afs_protocol_error(call, -EBADMSG);
xdr_decode_AFSCallBack_raw(&bp, call->reply[3]);
/* xdr_decode_AFSVolSync(&bp, call->reply[X]); */
@@ -814,8 +827,8 @@ static int afs_deliver_fs_remove(struct afs_call *call)

/* unmarshall the reply once we've received all of it */
bp = call->buffer;
- if (xdr_decode_AFSFetchStatus(call, &bp, &vnode->status, vnode,
- &call->expected_version, NULL) < 0)
+ if (afs_decode_status(call, &bp, &vnode->status, vnode,
+ &call->expected_version, NULL) < 0)
return afs_protocol_error(call, -EBADMSG);
/* xdr_decode_AFSVolSync(&bp, call->reply[X]); */

@@ -904,9 +917,9 @@ static int afs_deliver_fs_link(struct afs_call *call)

/* unmarshall the reply once we've received all of it */
bp = call->buffer;
- if (xdr_decode_AFSFetchStatus(call, &bp, &vnode->status, vnode, NULL, NULL) < 0 ||
- xdr_decode_AFSFetchStatus(call, &bp, &dvnode->status, dvnode,
- &call->expected_version, NULL) < 0)
+ if (afs_decode_status(call, &bp, &vnode->status, vnode, NULL, NULL) < 0 ||
+ afs_decode_status(call, &bp, &dvnode->status, dvnode,
+ &call->expected_version, NULL) < 0)
return afs_protocol_error(call, -EBADMSG);
/* xdr_decode_AFSVolSync(&bp, call->reply[X]); */

@@ -991,9 +1004,9 @@ static int afs_deliver_fs_symlink(struct afs_call *call)
/* unmarshall the reply once we've received all of it */
bp = call->buffer;
xdr_decode_AFSFid(&bp, call->reply[1]);
- if (xdr_decode_AFSFetchStatus(call, &bp, call->reply[2], NULL, NULL, NULL) ||
- xdr_decode_AFSFetchStatus(call, &bp, &vnode->status, vnode,
- &call->expected_version, NULL) < 0)
+ if (afs_decode_status(call, &bp, call->reply[2], NULL, NULL, NULL) ||
+ afs_decode_status(call, &bp, &vnode->status, vnode,
+ &call->expected_version, NULL) < 0)
return afs_protocol_error(call, -EBADMSG);
/* xdr_decode_AFSVolSync(&bp, call->reply[X]); */

@@ -1097,12 +1110,12 @@ static int afs_deliver_fs_rename(struct afs_call *call)

/* unmarshall the reply once we've received all of it */
bp = call->buffer;
- if (xdr_decode_AFSFetchStatus(call, &bp, &orig_dvnode->status, orig_dvnode,
- &call->expected_version, NULL) < 0)
+ if (afs_decode_status(call, &bp, &orig_dvnode->status, orig_dvnode,
+ &call->expected_version, NULL) < 0)
return afs_protocol_error(call, -EBADMSG);
if (new_dvnode != orig_dvnode &&
- xdr_decode_AFSFetchStatus(call, &bp, &new_dvnode->status, new_dvnode,
- &call->expected_version_2, NULL) < 0)
+ afs_decode_status(call, &bp, &new_dvnode->status, new_dvnode,
+ &call->expected_version_2, NULL) < 0)
return afs_protocol_error(call, -EBADMSG);
/* xdr_decode_AFSVolSync(&bp, call->reply[X]); */

@@ -1206,8 +1219,8 @@ static int afs_deliver_fs_store_data(struct afs_call *call)

/* unmarshall the reply once we've received all of it */
bp = call->buffer;
- if (xdr_decode_AFSFetchStatus(call, &bp, &vnode->status, vnode,
- &call->expected_version, NULL) < 0)
+ if (afs_decode_status(call, &bp, &vnode->status, vnode,
+ &call->expected_version, NULL) < 0)
return afs_protocol_error(call, -EBADMSG);
/* xdr_decode_AFSVolSync(&bp, call->reply[X]); */

@@ -1382,8 +1395,8 @@ static int afs_deliver_fs_store_status(struct afs_call *call)

/* unmarshall the reply once we've received all of it */
bp = call->buffer;
- if (xdr_decode_AFSFetchStatus(call, &bp, &vnode->status, vnode,
- &call->expected_version, NULL) < 0)
+ if (afs_decode_status(call, &bp, &vnode->status, vnode,
+ &call->expected_version, NULL) < 0)
return afs_protocol_error(call, -EBADMSG);
/* xdr_decode_AFSVolSync(&bp, call->reply[X]); */

@@ -2084,8 +2097,8 @@ static int afs_deliver_fs_fetch_status(struct afs_call *call)

/* unmarshall the reply once we've received all of it */
bp = call->buffer;
- xdr_decode_AFSFetchStatus(call, &bp, status, vnode,
- &call->expected_version, NULL);
+ afs_decode_status(call, &bp, status, vnode,
+ &call->expected_version, NULL);
callback[call->count].version = ntohl(bp[0]);
callback[call->count].expiry = ntohl(bp[1]);
callback[call->count].type = ntohl(bp[2]);
@@ -2196,9 +2209,9 @@ static int afs_deliver_fs_inline_bulk_status(struct afs_call *call)

bp = call->buffer;
statuses = call->reply[1];
- if (xdr_decode_AFSFetchStatus(call, &bp, &statuses[call->count],
- call->count == 0 ? vnode : NULL,
- NULL, NULL) < 0)
+ if (afs_decode_status(call, &bp, &statuses[call->count],
+ call->count == 0 ? vnode : NULL,
+ NULL, NULL) < 0)
return afs_protocol_error(call, -EBADMSG);

call->count++;
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