From: SeongJae Park sj@kernel.org
The advertisement of the persistent grants feature (writing 'feature-persistent' to xenbus) should mean not the decision for using the feature but only the availability of the feature. However, commit 74a852479c68 ("xen-blkfront: add a parameter for disabling of persistent grants") made a field of blkfront, which was a place for saving only the negotiation result, to be used for yet another purpose: caching of the 'feature_persistent' parameter value. As a result, the advertisement, which should follow only the parameter value, becomes inconsistent.
This commit fixes the misuse of the semantic by making blkfront saves the parameter value in a separate place and advertises the support based on only the saved value.
Fixes: 74a852479c68 ("xen-blkfront: add a parameter for disabling of persistent grants") Cc: stable@vger.kernel.org # 5.10.x Suggested-by: Juergen Gross jgross@suse.com Signed-off-by: SeongJae Park sj@kernel.org Tested-by: Marek Marczykowski-Górecki marmarek@invisiblethingslab.com Reviewed-by: Juergen Gross jgross@suse.com Link: https://lore.kernel.org/r/20220831165824.94815-3-sj@kernel.org Signed-off-by: Juergen Gross jgross@suse.com --- drivers/block/xen-blkfront.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c index 4e763701b372..276b2ee2a155 100644 --- a/drivers/block/xen-blkfront.c +++ b/drivers/block/xen-blkfront.c @@ -213,6 +213,9 @@ struct blkfront_info unsigned int feature_fua:1; unsigned int feature_discard:1; unsigned int feature_secdiscard:1; + /* Connect-time cached feature_persistent parameter */ + unsigned int feature_persistent_parm:1; + /* Persistent grants feature negotiation result */ unsigned int feature_persistent:1; unsigned int bounce:1; unsigned int discard_granularity; @@ -1848,7 +1851,7 @@ static int talk_to_blkback(struct xenbus_device *dev, goto abort_transaction; } err = xenbus_printf(xbt, dev->nodename, "feature-persistent", "%u", - info->feature_persistent); + info->feature_persistent_parm); if (err) dev_warn(&dev->dev, "writing persistent grants feature to xenbus"); @@ -2281,7 +2284,8 @@ static void blkfront_gather_backend_features(struct blkfront_info *info) if (xenbus_read_unsigned(info->xbdev->otherend, "feature-discard", 0)) blkfront_setup_discard(info);
- if (feature_persistent) + info->feature_persistent_parm = feature_persistent; + if (info->feature_persistent_parm) info->feature_persistent = !!xenbus_read_unsigned(info->xbdev->otherend, "feature-persistent", 0);