Hi This is a series of patches to prevent a crash when when someone is reading block device and block size is changed simultaneously. (the crash is already happening in the production environment)
The first patch adds a rw-lock to struct block_device, but doesn't use the lock anywhere. The reason why I submit this as a separate patch is that on my computer adding an unused field to this structure affects performance much more than any locking changes. The second patch uses the rw-lock. The lock is locked for read when doing I/O on the block device and it is locked for write when changing block size. The third patch converts the rw-lock to a percpu rw-lock for better performance, to avoid cache line bouncing. The fourth patch is an alternate percpu rw-lock implementation using RCU by Eric Dumazet. It avoids any atomic instruction in the hot path. Mikulas -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
