Introduce super_block.s_more_io_wait to park inodes that for some reason cannot
be synced immediately. They will be revisited in the next s_io enqueue time(<=5s).
The new data flow after this patchset:
s_dirty --> s_io --> s_more_io/s_more_io_wait --+
^ |
| |
+----------------------------------+
- to fill s_io:
s_more_io +
s_dirty(expired) +
s_more_io_wait
---> s_io
- to drain s_io:
s_io -+--> clean inodes goto inode_in_use/inode_unused
|
+--> s_more_io
|
+--> s_more_io_wait
Obviously there're no ordering or starvation problems in the queues:
- s_dirty is now a strict FIFO queue
- inode.dirtied_when is only set when made dirty
- once exipired, the dirty inode will stay in s_*io* queues until made clean
- the dirty inodes in s_*io* will be revisted in order, hence small files won't
be starved by big dirty files.
Cc: Michael Rubin <mrubin@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Signed-off-by: Fengguang Wu <wfg@xxxxxxxxxxxxxxxx>
---
fs/fs-writeback.c | 16 +++++++++++++---
fs/super.c | 1 +
include/linux/fs.h | 1 +
3 files changed, 15 insertions(+), 3 deletions(-)
--- linux-mm.orig/fs/fs-writeback.c
+++ linux-mm/fs/fs-writeback.c
@@ -172,6 +172,14 @@ static void requeue_io(struct inode *ino
list_move(&inode->i_list, &inode->i_sb->s_more_io);
}
+/*
+ * The inode should be retried after _sleeping_ for a while.
+ */
+static void requeue_io_wait(struct inode *inode)
+{
+ list_move(&inode->i_list, &inode->i_sb->s_more_io_wait);
+}
+
static void inode_sync_complete(struct inode *inode)
{
/*
@@ -206,13 +214,15 @@ static void queue_io(struct super_block
{
list_splice_init(&sb->s_more_io, sb->s_io.prev);
move_expired_inodes(&sb->s_dirty, &sb->s_io, older_than_this);
+ list_splice_init(&sb->s_more_io_wait, sb->s_io.prev);
}
int sb_has_dirty_inodes(struct super_block *sb)
{
- return !list_empty(&sb->s_dirty) ||
- !list_empty(&sb->s_io) ||
- !list_empty(&sb->s_more_io);
+ return !list_empty(&sb->s_dirty) ||
+ !list_empty(&sb->s_io) ||
+ !list_empty(&sb->s_more_io) ||
+ !list_empty(&sb->s_more_io_wait);
}
EXPORT_SYMBOL(sb_has_dirty_inodes);
--- linux-mm.orig/fs/super.c
+++ linux-mm/fs/super.c
@@ -64,6 +64,7 @@ static struct super_block *alloc_super(s
INIT_LIST_HEAD(&s->s_dirty);
INIT_LIST_HEAD(&s->s_io);
INIT_LIST_HEAD(&s->s_more_io);
+ INIT_LIST_HEAD(&s->s_more_io_wait);
INIT_LIST_HEAD(&s->s_files);
INIT_LIST_HEAD(&s->s_instances);
INIT_HLIST_HEAD(&s->s_anon);
--- linux-mm.orig/include/linux/fs.h
+++ linux-mm/include/linux/fs.h
@@ -1011,6 +1011,7 @@ struct super_block {
struct list_head s_dirty; /* dirty inodes */
struct list_head s_io; /* parked for writeback */
struct list_head s_more_io; /* parked for more writeback */
+ struct list_head s_more_io_wait; /* parked for sleep-then-retry */
struct hlist_head s_anon; /* anonymous dentries for (nfs) exporting */
struct list_head s_files;
--
-
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