[Bug 2156722] [NEW] raid1 write-mostly

Public bug reported: Kernel 6.8 broke RAID1 write-mostly functionality. Specifically, the system crashes after 1-7 days of uptime. Setting one drive (of two) of a RAID1 array to write-mostly results in a system crash after about 1-7 days of uptime, usually after about a day or so. The first indicator of impending crash is that 'sync' (from shell) doesn't return. System at this point is still usable for a while - apps start and seem to function normally (probably due to buffering/caching writes in ram). After a short while the system freezes and a reset is required. Crash can occur even while the system is idling or in general not doing much in terms of I/O. In other words it does not seem to be related or connected to the intensity of activity, even though it was observed on both desktop and server machines (/ on RAID1). Issue is repeatable and reproducible by manually failing and removing one of the drives, then re-adding it with write-mostly enabled. Or fixed/worked-around by removing the write-mostly flag. It was first observed in kernel 6.8 on 24.04 LTS. Verified on 3 distinct machines with kernels up to 6.18. ** Affects: linux (Ubuntu) Importance: Undecided Status: New -- You received this bug notification because you are subscribed to linux in Ubuntu. Matching subscriptions: Bgg, Bmail, Nb https://bugs.launchpad.net/bugs/2156722 Title: raid1 write-mostly Status in linux package in Ubuntu: New Bug description: Kernel 6.8 broke RAID1 write-mostly functionality. Specifically, the system crashes after 1-7 days of uptime. Setting one drive (of two) of a RAID1 array to write-mostly results in a system crash after about 1-7 days of uptime, usually after about a day or so. The first indicator of impending crash is that 'sync' (from shell) doesn't return. System at this point is still usable for a while - apps start and seem to function normally (probably due to buffering/caching writes in ram). After a short while the system freezes and a reset is required. Crash can occur even while the system is idling or in general not doing much in terms of I/O. In other words it does not seem to be related or connected to the intensity of activity, even though it was observed on both desktop and server machines (/ on RAID1). Issue is repeatable and reproducible by manually failing and removing one of the drives, then re-adding it with write-mostly enabled. Or fixed/worked-around by removing the write-mostly flag. It was first observed in kernel 6.8 on 24.04 LTS. Verified on 3 distinct machines with kernels up to 6.18. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2156722/+subscriptions