On 1/7/12 5:23 PM, Andrei Popa wrote:
> Hello,
>
> ierdnac-hp ~ # cat /etc/fstab |grep discard
> /dev/sda3 / ext4
> discard,noatime,norelatime,barrier=0,errors=remount-ro,data=writeback
> 0 1
>
> ierdnac-hp ~ # tune2fs -l /dev/sda3|grep discard
> Default mount options: journal_data_writeback discard
>
> ierdnac-hp ~ # cat /proc/mounts |grep write
> /dev/root / ext4 rw,noatime,user_xattr,acl,barrier=0,data=writeback 0 0
>
>
What kernel?
If it's a recent kernel, here is the logic which controls whether to show it:
if (test_opt(sb, DISCARD) && !(def_mount_opts & EXT4_DEFM_DISCARD))
seq_puts(seq, ",discard");
i.e. if "discard" is in the default mount options for the fs, it is not
shown, by design - although I am not 100% sure why that design decision
was made; that logic was explicitly added here:
commit 8b67f04ab9de5d8f3a71aef72bf02c995a506db5
Author: Theodore Ts'o <tytso@xxxxxxx>
Date: Sun Aug 1 23:14:20 2010 -0400
ext4: Add mount options in superblock
Allow mount options to be stored in the superblock. Also add default
mount option bits for nobarrier, block_validity, discard, and nodelalloc.
Signed-off-by: "Theodore Ts'o" <tytso@xxxxxxx>
which contained:
- if (test_opt(sb, DISCARD))
+ if (test_opt(sb, DISCARD) && !(def_mount_opts & EXT4_DEFM_DISCARD))
seq_puts(seq, ",discard");
so maybe Ted can speak to the reasoning behind it; I think the general philosophy
is to not show any defaults in /proc/mounts.
Thanks,
-Eric
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