Patch "devlink: Fix devlink parallel commands processing" has been added to the 6.8-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

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

    devlink: Fix devlink parallel commands processing

to the 6.8-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:
     devlink-fix-devlink-parallel-commands-processing.patch
and it can be found in the queue-6.8 subdirectory.

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



commit 600dfaeae16dc6da153e75658cc41305070fb72f
Author: Shay Drory <shayd@xxxxxxxxxx>
Date:   Tue Mar 12 12:52:38 2024 +0200

    devlink: Fix devlink parallel commands processing
    
    [ Upstream commit d7d75124965aee23e5e4421d78376545cf070b0a ]
    
    Commit 870c7ad4a52b ("devlink: protect devlink->dev by the instance
    lock") added devlink instance locking inside a loop that iterates over
    all the registered devlink instances on the machine in the pre-doit
    phase. This can lead to serialization of devlink commands over
    different devlink instances.
    
    For example: While the first devlink instance is executing firmware
    flash, all commands to other devlink instances on the machine are
    forced to wait until the first devlink finishes.
    
    Therefore, in the pre-doit phase, take the devlink instance lock only
    for the devlink instance the command is targeting. Devlink layer is
    taking a reference on the devlink instance, ensuring the devlink->dev
    pointer is valid. This reference taking was introduced by commit
    a380687200e0 ("devlink: take device reference for devlink object").
    Without this commit, it would not be safe to access devlink->dev
    lockless.
    
    Fixes: 870c7ad4a52b ("devlink: protect devlink->dev by the instance lock")
    Signed-off-by: Shay Drory <shayd@xxxxxxxxxx>
    Reviewed-by: Jiri Pirko <jiri@xxxxxxxxxx>
    Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/net/devlink/netlink.c b/net/devlink/netlink.c
index 499885c8b9cae..593605c1b1ef4 100644
--- a/net/devlink/netlink.c
+++ b/net/devlink/netlink.c
@@ -193,12 +193,13 @@ devlink_get_from_attrs_lock(struct net *net, struct nlattr **attrs,
 	devname = nla_data(attrs[DEVLINK_ATTR_DEV_NAME]);
 
 	devlinks_xa_for_each_registered_get(net, index, devlink) {
-		devl_dev_lock(devlink, dev_lock);
-		if (devl_is_registered(devlink) &&
-		    strcmp(devlink->dev->bus->name, busname) == 0 &&
-		    strcmp(dev_name(devlink->dev), devname) == 0)
-			return devlink;
-		devl_dev_unlock(devlink, dev_lock);
+		if (strcmp(devlink->dev->bus->name, busname) == 0 &&
+		    strcmp(dev_name(devlink->dev), devname) == 0) {
+			devl_dev_lock(devlink, dev_lock);
+			if (devl_is_registered(devlink))
+				return devlink;
+			devl_dev_unlock(devlink, dev_lock);
+		}
 		devlink_put(devlink);
 	}