Hi all, First of all apologies if this is the wrong place to send this report, this looked like the right area. I recently updated my Linux workstation to Ubuntu 14.04, which came with the Linux 3.13 kernel. This meant bcache became available to try out. I installed bcache-tools from the PPA at https://launchpad.net/~g2p/+archive/storage/ After installing bcache-tools and rebooting, I noticed considerable lag when starting up the workstation. Looking in /var/log/dmesg I saw pauses like this: [ 3.256014] ata6: SATA link up 3.0 Gbps (SStatus 123 SControl 300) [ 3.291801] ata6.00: ATA-7: WDC WD4000AAKS-00TMA0, 12.01C01, max UDMA/133 [ 3.291804] ata6.00: 781422768 sectors, multi 0: LBA48 [ 3.292659] ata6.00: configured for UDMA/133 [ 3.292750] scsi 5:0:0:0: Direct-Access ATA WDC WD4000AAKS-0 12.0 PQ: 0 ANSI: 5 [ 3.292898] sd 5:0:0:0: Attached scsi generic sg7 type 0 [ 3.292899] sd 5:0:0:0: [sdg] 781422768 512-byte logical blocks: (400 GB/372 GiB) [ 3.292942] sd 5:0:0:0: [sdg] Write Protect is off [ 3.292945] sd 5:0:0:0: [sdg] Mode Sense: 00 3a 00 00 [ 3.292964] sd 5:0:0:0: [sdg] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA [ 3.358883] sdg: sdg1 sdg2 sdg3 < sdg5 sdg6 sdg7 sdg8 > [ 3.359236] sd 5:0:0:0: [sdg] Attached SCSI disk [ 4.022378] random: nonblocking pool is initialized [ 13.284572] end_request: I/O error, dev fd0, sector 0 [ 25.444523] end_request: I/O error, dev fd0, sector 0 [ 25.444526] Buffer I/O error on device fd0, logical block 0 [ 32.749886] EXT4-fs (sda1): mounted filesystem with ordered data mode. Opts: (null) [ 32.878527] init: ureadahead main process (264) terminated with status 5 Tracing this back, I noticed that bcache-tools installs a new script in /lib/udev/rules.d/ to look for the bcache superblock. It looks for this on all block devices, including the floppy drive (/dev/fd0) on my workstation. I ran the command line to see how /dev/fd0 appears to udev: udevadm info -a -p $(udevadm info -q path -n /dev/fd0) The results look like this: looking at device '/devices/platform/floppy.0/block/fd0': KERNEL=="fd0" SUBSYSTEM=="block" DRIVER=="" ATTR{ro}=="0" ATTR{size}=="0" ATTR{stat}==" 0 0 0 0 0 0 0 0 0 0 0" ATTR{range}=="1" ATTR{discard_alignment}=="0" ATTR{events}=="" ATTR{ext_range}=="1" ATTR{events_poll_msecs}=="2000" ATTR{alignment_offset}=="0" ATTR{inflight}==" 0 0" ATTR{removable}=="1" ATTR{capability}=="11" ATTR{events_async}=="" looking at parent device '/devices/platform/floppy.0': KERNELS=="floppy.0" SUBSYSTEMS=="platform" DRIVERS=="floppy" ATTRS{cmos}=="4" looking at parent device '/devices/platform': KERNELS=="platform" SUBSYSTEMS=="" DRIVERS=="" To avoid checking the floppy drive, I made a change to explicitly filter out block devices whose DRIVERS matches floppy. Doing this directly in /lib/udev/rules.d/ is discouraged, so I copied it and modified it in /etc/udev/rules.d/ instead. This patch to 69-bcache.rules performs this filter: ------ diff --git a/69-bcache.rules b/69-bcache.rules index b83f6bc..bddf309 100644 --- a/69-bcache.rules +++ b/69-bcache.rules @@ -2,6 +2,8 @@ # man 7 udev for syntax SUBSYSTEM!="block", GOTO="bcache_end" +DRIVERS=="floppy", GOTO="bcache_end" +# KERNEL=="fd[0-9]*", GOTO="bcache_end" ACTION=="remove", GOTO="bcache_end" # blkid was run by the standard udev rules ------ Note that I also tried using a KERNEL match for fd0 etc, but looking at the DRIVERS line seemed more correct. (Am I right?) Making this change and rebooting the system made most pauses disappear. One pause remained, which was the one immediately after BIOS POST, before the Ubuntu startup screen appears. Digging a little further revealed the /usr/share/initramfs-tools/hooks/ directory, and the bcache hook script in there. Here the problem was that the modified script I'd put in /etc/udev/rules.d/ doesn't get copied into the initramfs image. Looking around a few of the other hook scripts in this directory, and seeing how they handle custom udev rules, I changed the bcache hook to check and copy the bcache udev rules file from /etc/udev/rules.d/ if present, otherwise copying from /lib/udev/rules.d/ instead. This patch fixes that behaviour: ------ diff --git a/initramfs/hook b/initramfs/hook index e618e1a..a6baa24 100755 --- a/initramfs/hook +++ b/initramfs/hook @@ -16,7 +16,12 @@ esac . /usr/share/initramfs-tools/hook-functions -cp -pt "${DESTDIR}/lib/udev/rules.d" /lib/udev/rules.d/69-bcache.rules +if [ -e /etc/udev/rules.d/69-bcache.rules ]; then + cp -pt "${DESTDIR}/lib/udev/rules.d" /etc/udev/rules.d/69-bcache.rules +elif [ -e /lib/udev/rules.d/69-bcache.rules ]; then + cp -pt "${DESTDIR}/lib/udev/rules.d" /lib/udev/rules.d/69-bcache.rules +fi + copy_exec /lib/udev/bcache-register copy_exec /lib/udev/probe-bcache manual_add_modules bcache ------ It would be good if one, or even both, of these changes could be made to the bcache-tools repository, or at least the bcache-tools PPA for Ubuntu. This would make setting up bcache easier to maintain in the future. Best regards, Nicholas. -- To unsubscribe from this list: send the line "unsubscribe linux-bcache" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
