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Re: [Xen-devel] [PATCH RESEND] xen/blkfront: improve protection against issuing unsupported REQ_FUA

On 12/01/2014 08:01 AM, Vitaly Kuznetsov wrote:
Guard against issuing unsupported REQ_FUA and REQ_FLUSH was introduced
in d11e61583 and was factored out into blkif_request_flush_valid() in
0f1ca65ee. However:
1) This check in incomplete. In case we negotiated to feature_flush = REQ_FLUSH
    and flush_op = BLKIF_OP_FLUSH_DISKCACHE (so FUA is unsupported) FUA request
    will still pass the check.
2) blkif_request_flush_valid() is misnamed. It is bool but returns true when
    the request is invalid.
3) When blkif_request_flush_valid() fails -EIO is being returned. It seems that
    -EOPNOTSUPP is more appropriate here.
Fix all of the above issues.

This patch is based on the original patch by Laszlo Ersek and a comment by
Jeff Moyer.

Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
Reviewed-by: Laszlo Ersek <lersek@xxxxxxxxxx>

Reviewed-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>

(although, as I mentioned last time, a companion patch to remove flush_op would be a good thing to have)


  drivers/block/xen-blkfront.c | 14 ++++++++------
  1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index 5ac312f..2e6c103 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -582,12 +582,14 @@ static inline void flush_requests(struct blkfront_info 
-static inline bool blkif_request_flush_valid(struct request *req,
-                                            struct blkfront_info *info)
+static inline bool blkif_request_flush_invalid(struct request *req,
+                                              struct blkfront_info *info)
        return ((req->cmd_type != REQ_TYPE_FS) ||
-               ((req->cmd_flags & (REQ_FLUSH | REQ_FUA)) &&
-               !info->flush_op));
+               ((req->cmd_flags & REQ_FLUSH) &&
+                !(info->feature_flush & REQ_FLUSH)) ||
+               ((req->cmd_flags & REQ_FUA) &&
+                !(info->feature_flush & REQ_FUA)));
@@ -612,8 +614,8 @@ static void do_blkif_request(struct request_queue *rq)
blk_start_request(req); - if (blkif_request_flush_valid(req, info)) {
-                       __blk_end_request_all(req, -EIO);
+               if (blkif_request_flush_invalid(req, info)) {
+                       __blk_end_request_all(req, -EOPNOTSUPP);

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