f2fs: Add option to limit required GC for checkpoint=disable
This extends the checkpoint option to allow checkpoint=disable:%u[%]
This allows you to specify what how much of the disk you are willing
to lose access to while mounting with checkpoint=disable. If the amount
lost would be higher, the mount will return -EAGAIN. This can be given
as a percent of total space, or in blocks.
Currently, we need to run garbage collection until the amount of holes
is smaller than the OVP space. With the new option, f2fs can mark
space as unusable up front instead of requiring garbage collection until
the number of holes is small enough.
Signed-off-by: Daniel Rosenberg <drosen@google.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
diff --git a/Documentation/filesystems/f2fs.txt b/Documentation/filesystems/f2fs.txt
index 66aca04..bebd1be 100644
--- a/Documentation/filesystems/f2fs.txt
+++ b/Documentation/filesystems/f2fs.txt
@@ -214,11 +214,22 @@
non-atomic files likewise "nobarrier" mount option.
test_dummy_encryption Enable dummy encryption, which provides a fake fscrypt
context. The fake fscrypt context is used by xfstests.
-checkpoint=%s Set to "disable" to turn off checkpointing. Set to "enable"
+checkpoint=%s[:%u[%]] Set to "disable" to turn off checkpointing. Set to "enable"
to reenable checkpointing. Is enabled by default. While
disabled, any unmounting or unexpected shutdowns will cause
the filesystem contents to appear as they did when the
filesystem was mounted with that option.
+ While mounting with checkpoint=disabled, the filesystem must
+ run garbage collection to ensure that all available space can
+ be used. If this takes too much time, the mount may return
+ EAGAIN. You may optionally add a value to indicate how much
+ of the disk you would be willing to temporarily give up to
+ avoid additional garbage collection. This can be given as a
+ number of blocks, or as a percent. For instance, mounting
+ with checkpoint=disable:100% would always succeed, but it may
+ hide up to all remaining free space. The actual space that
+ would be unusable can be viewed at /sys/fs/f2fs/<disk>/unusable
+ This space is reclaimed once checkpoint=enable.
================================================================================
DEBUGFS ENTRIES
@@ -396,6 +407,12 @@
current_reserved_blocks This shows # of blocks currently reserved.
+ unusable If checkpoint=disable, this shows the number of
+ blocks that are unusable.
+ If checkpoint=enable it shows the number of blocks
+ that would be unusable if checkpoint=disable were
+ to be set.
+
================================================================================
USAGE
================================================================================