Hello.
I am running the Fedora 21 beta on an SSD with /boot and / on XFS. I want to add the discard mount option to both of them, so I changed defaults to defaults,discard in /etc/fstab and rebooted. While /boot was mounted with the discard option / was not.
This is my /etc/fstab, actual uuids redacted:
UUID=... / xfs defaults,discard 0 0 UUID=... /boot xfs defaults,discard 0 0 UUID=... /boot/efi vfat umask=0077,shortname=winnt 0 0 UUID=... swap swap defaults 0 0
I tried rebuilding the initramfs with dracut -fv, but after a reboot still only /boot is mounted with the discard option.
# grep discard /proc/mounts /dev/sda2 /boot xfs rw,seclabel,relatime,attr2,discard,inode64,noquota 0 0
The rest of the file systems look like this:
# grep ^/ /proc/mounts /dev/sda4 / xfs rw,seclabel,relatime,attr2,inode64,noquota 0 0 /dev/sda2 /boot xfs rw,seclabel,relatime,attr2,discard,inode64,noquota 0 0 /dev/sda1 /boot/efi vfat rw,relatime,fmask=0077,dmask=0077,codepage=437,iocharset=ascii,shortname=winnt,errors=remount-ro 0 0
How do I mount / with the correct options?
J
On Sun, 2014-11-23 at 11:06 +0100, John Tall wrote:
Hello.
I am running the Fedora 21 beta on an SSD with /boot and / on XFS. I want to add the discard mount option to both of them, so I changed defaults to defaults,discard in /etc/fstab and rebooted. While /boot was mounted with the discard option / was not.
Is / an LV?
On Sun, Nov 23, 2014 at 5:43 PM, Adam Williamson adamwill@fedoraproject.org wrote:
On Sun, 2014-11-23 at 11:06 +0100, John Tall wrote:
Hello.
I am running the Fedora 21 beta on an SSD with /boot and / on XFS. I want to add the discard mount option to both of them, so I changed defaults to defaults,discard in /etc/fstab and rebooted. While /boot was mounted with the discard option / was not.
Is / an LV?
No. They are both regular GPT partitions.
J
On Sun, Nov 23, 2014 at 12:27 PM, John Tall mjtallx@gmail.com wrote:
No. They are both regular GPT partitions.
What results do you get for: # journalctl -b -l -o short-monotonic | grep -i discard
That may reveal the attempt to (re)mount sysroot with discard and why it failed. If nothing comes up then boot debug options need to set.
See if this works while you're at it: # mount -o remount,discard /
And then check mounts. It should now show discard is enabled.
And while you're at it confirm this: # sgdisk -i4 /dev/sda
"partition GUID code" should be 0fc63daf-8483-4772-8e79-3d69d8477de4, if you use one of the freedesktop discoverable partitions partitiontypeGUIDs then systemd ignores fstab for that partition and does its own automount.
Also FWIW discard isn't a good mount option to use for most SSDs with non-queuable trim support. If it's one of the very newest SSDs supporting queuable trim then it should be fine to set. Otherwise you're better off with a weekly cron issuing fstrim.
On Sun, Nov 23, 2014 at 8:59 PM, Chris Murphy lists@colorremedies.com wrote:
On Sun, Nov 23, 2014 at 12:27 PM, John Tall mjtallx@gmail.com wrote:
No. They are both regular GPT partitions.
What results do you get for: # journalctl -b -l -o short-monotonic | grep -i discard
That may reveal the attempt to (re)mount sysroot with discard and why it failed. If nothing comes up then boot debug options need to set.
Not much, only two lines about the /boot partition.
[ 27.339461] host1 systemd[1]: About to execute: /bin/mount -n /dev/disk/by-uuid/25692e3e-42cd-1923-bcd4-d3511ac23512 /boot -t xfs -o defaults,discard [ 27.341034] host1 systemd[507]: Executing: /bin/mount -n /dev/disk/by-uuid/25692e3e-42cd-1923-bcd4-d3511ac23512 /boot -t xfs -o defaults,discard
See if this works while you're at it: # mount -o remount,discard /
And then check mounts. It should now show discard is enabled.
Unfortunately not, it does not show discard in /proc/mounts.
And while you're at it confirm this: # sgdisk -i4 /dev/sda
"partition GUID code" should be 0fc63daf-8483-4772-8e79-3d69d8477de4, if you use one of the freedesktop discoverable partitions partitiontypeGUIDs then systemd ignores fstab for that partition and does its own automount.
The partition GUID code is as expected 0FC63DAF-8483-4772-8E79-3D69D8477DE4. Same with -i2, the /boot partition.
Also FWIW discard isn't a good mount option to use for most SSDs with non-queuable trim support. If it's one of the very newest SSDs supporting queuable trim then it should be fine to set. Otherwise you're better off with a weekly cron issuing fstrim.
OK. Good tip! I'll do some testing if I can get discard working and keep that in mind.
J
On Sun, Nov 23, 2014 at 3:06 PM, John Tall mjtallx@gmail.com wrote:
See if this works while you're at it: # mount -o remount,discard /
And then check mounts. It should now show discard is enabled.
Unfortunately not, it does not show discard in /proc/mounts.
Ed Greshko points to the cause for this, looks like discard can't be added with remount. So now I think I know what's going on:
Systemd mounts the root device read only at /sysroot, and only then can it read fstab to know what the mount options are. It then remounts rw and includes the mount options in fstab. So any options that aren't supported by remount, won't work.
What's odd is that I'm certain discard worked for root on Btrfs, so I wonder if this remount limitation is XFS only or if it applies to any filesystem? In which case, how is anyone getting trim to work on the root device?
The only answer I'm thinking of is pretty obscure: use boot parameter rootflags=discard. The rootflags= parameter accepts mount options and applies them to the volume defined by root=. I only know this because Btrfs installs depend on rootflags=subvol=<rootname> to mount the correct subvolume containing root, and subvol=<name> is just a repeat of what's in fstab (typically).
On 11/23/2014 05:23 PM, Chris Murphy wrote:
What's odd is that I'm certain discard worked for root on Btrfs, so I wonder if this remount limitation is XFS only or if it applies to any filesystem? In which case, how is anyone getting trim to work on the root device?
Limitation of xfs only.
On Sun, Nov 23, 2014 at 5:37 PM, Michael Cronenworth mike@cchtml.com wrote:
On 11/23/2014 05:23 PM, Chris Murphy wrote:
What's odd is that I'm certain discard worked for root on Btrfs, so I wonder if this remount limitation is XFS only or if it applies to any filesystem? In which case, how is anyone getting trim to work on the root device?
Limitation of xfs only.
OK. rootflags=discard should still work since it's issued at the first mount.
Chris Murphy
On Mon, Nov 24, 2014 at 12:23 AM, Chris Murphy lists@colorremedies.com wrote:
On Sun, Nov 23, 2014 at 3:06 PM, John Tall mjtallx@gmail.com wrote:
See if this works while you're at it: # mount -o remount,discard /
And then check mounts. It should now show discard is enabled.
Unfortunately not, it does not show discard in /proc/mounts.
Ed Greshko points to the cause for this, looks like discard can't be added with remount. So now I think I know what's going on:
Systemd mounts the root device read only at /sysroot, and only then can it read fstab to know what the mount options are. It then remounts rw and includes the mount options in fstab. So any options that aren't supported by remount, won't work.
What's odd is that I'm certain discard worked for root on Btrfs, so I wonder if this remount limitation is XFS only or if it applies to any filesystem? In which case, how is anyone getting trim to work on the root device?
The only answer I'm thinking of is pretty obscure: use boot parameter rootflags=discard. The rootflags= parameter accepts mount options and applies them to the volume defined by root=. I only know this because Btrfs installs depend on rootflags=subvol=<rootname> to mount the correct subvolume containing root, and subvol=<name> is just a repeat of what's in fstab (typically).
It worked after adding rootflags=discard to /etc/default/grub and running grub2-mkconfig. Thanks for the help!
J
On 11/23/14 18:06, John Tall wrote:
Hello.
I am running the Fedora 21 beta on an SSD with /boot and / on XFS. I want to add the discard mount option to both of them, so I changed defaults to defaults,discard in /etc/fstab and rebooted. While /boot was mounted with the discard option / was not.
This is my /etc/fstab, actual uuids redacted:
UUID=... / xfs defaults,discard 0 0 UUID=... /boot xfs defaults,discard 0 0 UUID=... /boot/efi vfat umask=0077,shortname=winnt 0 0 UUID=... swap swap defaults 0 0
I tried rebuilding the initramfs with dracut -fv, but after a reboot still only /boot is mounted with the discard option.
# grep discard /proc/mounts /dev/sda2 /boot xfs rw,seclabel,relatime,attr2,discard,inode64,noquota 0 0
The rest of the file systems look like this:
# grep ^/ /proc/mounts /dev/sda4 / xfs rw,seclabel,relatime,attr2,inode64,noquota 0 0 /dev/sda2 /boot xfs rw,seclabel,relatime,attr2,discard,inode64,noquota 0 0 /dev/sda1 /boot/efi vfat rw,relatime,fmask=0077,dmask=0077,codepage=437,iocharset=ascii,shortname=winnt,errors=remount-ro 0 0
How do I mount / with the correct options?
J
Maybe you're seeing this?
https://bbs.archlinux.org/viewtopic.php?id=143254
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Adam Williamson -
Chris Murphy -
Ed Greshko -
John Tall -
Michael Cronenworth