From: Jun'ichi Nomura Date: Fri, 26 Jan 2007 08:57:07 +0000 (-0800) Subject: [PATCH] dm-multipath: fix stall on noflush suspend/resume X-Git-Tag: v2.6.20-rc7~68 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=bfa152fa5e4d328fe3ebf15908ee8ec20a0ce6dc;p=pandora-kernel.git [PATCH] dm-multipath: fix stall on noflush suspend/resume Allow noflush suspend/resume of device-mapper device only for the case where the device size is unchanged. Otherwise, dm-multipath devices can stall when resumed if noflush was used when suspending them, all paths have failed and queue_if_no_path is set. Explanation: 1. Something is doing fsync() on the block dev, holding inode->i_sem 2. The fsync write is blocked by all-paths-down and queue_if_no_path 3. Someone requests to suspend the dm device with noflush. Pending writes are left in queue. 4. In the middle of dm_resume(), __bind() tries to get inode->i_sem to do __set_size() and waits forever. 'noflush suspend' is a new device-mapper feature introduced in early 2.6.20. So I hope the fix being included before 2.6.20 is released. Example of reproducer: 1. Create a multipath device by dmsetup 2. Fail all paths during mkfs 3. Do dmsetup suspend --noflush and load new map with healthy paths 4. Do dmsetup resume Signed-off-by: Jun'ichi Nomura Acked-by: Alasdair G Kergon Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Reading git-diff-tree failed