On 03/06/2013 12:13 AM, Lukáš Czerner wrote: > On Tue, 5 Mar 2013, Stephen Warren wrote: > >> Date: Tue, 5 Mar 2013 13:25:18 -0700 >> From: Stephen Warren <swarren@xxxxxxxxxxxxx> >> To: Theodore Ts'o <tytso@xxxxxxx> >> Cc: Chris Ball <cjb@xxxxxxxxxx>, linux-ext4@xxxxxxxxxxxxxxx, >> Stephen Warren <swarren@xxxxxxxxxx> >> Subject: [PATCH] mke2fs: restore verbose message for BLKDISCARD >> >> From: Stephen Warren <swarren@xxxxxxxxxx> >> >> mke2fs on a large slow eMMC device may appear to hang while executing >> ioctl(BLKDISCARD). CTRL-C and CTRL-\ don't appear to respond, or respond >> extremely slowly. -v doesn't give any hints what's happening. Only strace >> is a clue. Make -v print some clues to make it easier to track down the >> apparent hang. >> >> This change re-uses the original messages that were implemented as part >> of 5827d24 "mke2fs support for BLKDISCARD" in order to easily re-use the >> translations of that message. Note that this patch prints the first >> message before executing the IOCTL, so the user is told what's going on >> before the long wait. >> >> Signed-off-by: Stephen Warren <swarren@xxxxxxxxxx> > > Note that you've added the message only around the first 4k discard > which is only used to test whether the device actually support the > discard... which is not very useful and it can not even know whether > the whole device discard will succeed/fail so it is misleading. Oops. I certainly should looked at the code better. > Moreover there actually is a message saying that we're "Discarding > device blocks" and it even shows the progress. The step in which > we're doing the discard (and update the progress) is given by > DISCARD_STEP_MB = 2048MB. And all that in non verbose mode as well. That said, it's that very first call to io_channel_discard() that is hanging then; I don't see the existing message at all. With my change, I do see the new message that I added. (So, no stdio flushing issue here). I will go investigate why this API is hanging. Sorry for the noise. ... > As mentioned we're doing 2GB discard steps so the problem really > should not be on mkfs side. It is very much possible that the > discard implementation on the eMMC is terribly slow (which does not > surprise me). What is says about itself ? > > grep . /sys/block/sda/queue/discard_* /sys/block/mmcblk1/queue/discard_granularity 0 /sys/block/mmcblk1/queue/discard_max_bytes 512 /sys/block/mmcblk1/queue/discard_zeroes_data 1 -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
