nilfs-utils: nilfs-clean add cmdline param min-reclaimable-blocks

This patch adds a command line parameter for nilfs-clean to allow
the manual override of the min_reclaimable_blocks option.

Signed-off-by: Andreas Rohner <andreas.rohner@gmx.net>
nilfs-utils: add suport for NILFS_IOCTL_SET_SUINFO ioctl

This patch adds library support for the NILFS_IOCTL_SET_SUINFO
ioctl. A new function nilfs_set_suinfo and the structure
nilfs_suinfo_update, which contains the update information, are
added.

With this function the segment usage information can be updated
from userspace, which can be used as a shortcut for certain GC
operations.

Signed-off-by: Andreas Rohner <andreas.rohner@gmx.net>
nilfs-utils: add optimized version of nilfs_xreclaim_segments

This patch adds an additional parameter min_reclaimable_blks to
the nilfs_reclaim_params structure. This parameter specifies the
minimum number of reclaimable blocks in a segment, before it can be
cleaned. If a segment is below this threshold, it is considered to
be not worth cleaning, because all the live blocks would need to be
moved to a new segment, which is expensive, and the number of
reclaimable blocks is too low. But it is still necessary to update
the segment usage information to turn the old segment into a new
one.

This is basically a shortcut to cleaning the segment. It is still
necessary to read the segment summary information, but the writing
of the live blocks can be skipped if it's not worth it.

This optimization can be enabled and disabled by the
use_set_suinfo switch in the configuration file. If the kernel
doesn't support the set_suinfo ioctl it returns the error
number ENOTTY, which also permanently disables the optimization.

Signed-off-by: Andreas Rohner <andreas.rohner@gmx.net>
nilfs-utils: add a no_timeout flag to enable faster loop

This patch adds a flag, that enables the GC to skip the timeout in
certain situations. For example if the cleaning of some segments
was deferred to a later time, then no real progress has been
made. Apart from reading a few summary blocks, no data was read or
written to disk. In this situation it makes sense to skip the
normal timeout once and immediately try to clean the next set of
segments.

Unfortunately it is not possible, to directly continue the cleaning
loop, because this would lead to an unresponsive GC process.
Therefore the timeout is simply set to 0 seconds.

Signed-off-by: Andreas Rohner <andreas.rohner@gmx.net>