path: root/Documentation
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authorAndreas Rohner <andreas.rohner@gmx.net>2014-04-03 14:50:28 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2014-04-03 16:21:25 -0700
commit2cc88f3a5f16ae9a3c8f54de1b2fd4a397b36075 (patch)
treeeccf104b99fbaca714acd78ebe90b574f408f0fe /Documentation
parent00e9ffcd27cc5d0af9076383c6242c32335546f8 (diff)
nilfs2: implementation of NILFS_IOCTL_SET_SUINFO ioctl
With this ioctl the segment usage entries in the SUFILE can be updated from userspace. This is useful, because it allows the userspace GC to modify and update segment usage entries for specific segments, which enables it to avoid unnecessary write operations. If a segment needs to be cleaned, but there is no or very little reclaimable space in it, the cleaning operation basically degrades to a useless moving operation. In the end the only thing that changes is the location of the data and a timestamp in the segment usage information. With this ioctl the GC can skip the cleaning and update the segment usage entries directly instead. 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. [konishi.ryusuke@lab.ntt.co.jp: add description of NILFS_IOCTL_SET_SUINFO ioctl] Signed-off-by: Andreas Rohner <andreas.rohner@gmx.net> Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation')
1 files changed, 7 insertions, 0 deletions
diff --git a/Documentation/filesystems/nilfs2.txt b/Documentation/filesystems/nilfs2.txt
index 06887d46ccf..8b887ae4e39 100644
--- a/Documentation/filesystems/nilfs2.txt
+++ b/Documentation/filesystems/nilfs2.txt
@@ -111,6 +111,13 @@ Table of NILFS2 specific ioctls
nilfs_resize utilities and by nilfs_cleanerd
+ NILFS_IOCTL_SET_SUINFO Modify segment usage info of requested
+ segments. This ioctl is used by
+ nilfs_cleanerd daemon to skip unnecessary
+ cleaning operation of segments and reduce
+ performance penalty or wear of flash device
+ due to redundant move of in-use blocks.
NILFS_IOCTL_GET_SUSTAT Return segment usage statistics. This ioctl
is used in lssu, nilfs_resize utilities and
by nilfs_cleanerd daemon.