Il 24/08/2012 09:26, Artem Bityutskiy ha scritto:
From: Artem Bityutskiy <artem.bityutskiy@xxxxxxxxxxxxxxx> Currently the emergency remount (triggered by Sysrq-u) re-mounting only those file-systems R/O, which have an associated block device (sb->s_bdev). This does not work for file-systems like UBIFS and JFFS2 which work on top of MTD devices (character devices) and always have sb->s_bdev = NULL. This also does not work for tmpfs. Most probably the intention was to avoid re-mounting R/O file-systems like procfs, sysfs, cgroup, and debugfs. However, I do not really see why not to remount them R/O as well in case of emergency. This patch removes the 'sb->s_bdev != NULL' check from 'do_emergency_remount()', so _all_ file-systems will be re-mounted R/O. Tested in Fedora - all file-systems (ext4, ubifs, procfs, sysfs, cgroup, and debugfs) become R/O on Sysrq-u with this patch. Signed-off-by: Artem Bityutskiy <artem.bityutskiy@xxxxxxxxxxxxxxx>
Does it make sense to remount r/o for example debugfs in this case? Maybe if there is something wrong I want enable something to catch debug info. Similar things for other pseudo-fs. Sure, the s_bdev seems a strong check. We could add a new flag to know if the emergency remount should be happen. It would give us the fs granularity, and maybe it could be turned on/off with the mount.
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