Description of problem: - Upgrading to kernel 3.18.3-201.fc21 breaks wifi connections - Previous good kernel is kernel-3.17.8-300.fc21 Version-Release number of selected component (if applicable): 3.18.3-201.fc21 How reproducible: - enable wifi - wifi appears as only "half connected": in the top-right panel in gnome shell, there is a question mark over the wifi symbol - choosing "select network" from wifi menu shows that the correct wifi network has a tick next to it, but no internet connection is available Steps to Reproduce: 1. assuming previous good kernel is running (kernel-3.17.8-300) 2. yum check-update 3. yum update kernel 4. reboot 5. running kernel is kernel-3.18.3-201 6. enable wifi from top-right menu in gnome-shell Actual results: wifi no longer works after booting with updated kernel Expected results: wifi connects and works Additional info: relevant lspci (from working kernel 3.17.8-300) 00:16.0 Communication controller: Intel Corporation 7 Series/C210 Series Chipset Family MEI Controller #1 (rev 04) 01:00.0 Network controller: Intel Corporation Centrino Advanced-N 6235 (rev 24) 02:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller (rev 06) $ lsmod | grep wifi iwlwifi 129618 1 iwldvm cfg80211 505401 3 iwlwifi,mac80211,iwldvm (lsmod is from working kernel 3.17.8-300)
Related bug: https://bugzilla.kernel.org/show_bug.cgi?id=92151
Please attach dmesg output from working and non-working kernel.
This turned out to be a problem with ext4 in kernel 3.18. My /etc/fstab had journal_async_commit for the root partition. Apparently the journal_async_commit option cannot be enabled during a remount. As the root partition is already mounted by the time it reads /etc/fstab, the ext4 driver in 3.18 sees journal_async_commit and "helpfully" remounts root as read-only. This in turn causes wifi to break. This is arguably boneheaded behaviour on the part of the ext4 driver. The real fix is to have a more strict kernel patch review process, in order prevent such boneheaded behaviour ending up in the kernel. https://bugzilla.redhat.com/show_bug.cgi?id=1190933
I don't know how wifi problem could possibly depend on ext4 problem. Can we get info requested in comment 2 ?
It's as simple as it sounds: ext4 has a bug which causes the root filesystem (/) to become read-only at boot. This in turn stops wifi connecting properly. I presume this is because NetworkManager (or a related subsystem) can't write to the root filesystem (maybe to the /etc directory?). By having journal_async_commit in /etc/fstab, I can reliably put the root filesystem into read-only at boot, and hence cause problems for wifi. Without journal_async_commit in /etc/fstab, wifi works properly. Removing journal_async_commit solves the issue for me, but it does point to the actual bug being in the ext4 driver.