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writeback, cgroup: support switching multiple inodes at once

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Currently only a single inode can be switched to another writeback
structure at once.  That means to switch an inode a separate
inode_switch_wbs_context structure must be allocated, and a separate rcu
callback and work must be scheduled.

It's fine for the existing ad-hoc switching, which is not happening that
often, but sub-optimal for massive switching required in order to release
a writeback structure.  To prepare for it, let's add a support for
switching multiple inodes at once.

Instead of containing a single inode pointer, inode_switch_wbs_context
will contain a NULL-terminated array of inode pointers.
inode_do_switch_wbs() will be called for each inode.

To optimize the locking bdi->wb_switch_rwsem, old_wb's and new_wb's
list_locks will be acquired and released only once altogether for all
inodes.  wb_wakeup() will be also be called only once.  Instead of calling
wb_put(old_wb) after each successful switch, wb_put_many() is introduced
and used.

Link: https://lkml.kernel.org/r/20210608230225.2078447-8-guro@fb.com
Signed-off-by: Roman Gushchin <guro@fb.com>
Acked-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Acked-by: Dennis Zhou <dennis@kernel.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Dave Chinner <dchinner@redhat.com>
Cc: Jan Kara <jack@suse.com>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Roman Gushchin
2021-06-28 19:35:59 -07:00
committed by Linus Torvalds
parent 72d4512e9c
commit f5fbe6b7ad
2 changed files with 80 additions and 44 deletions
Download Patch File Download Diff File Expand all files Collapse all files

18
include/linux/backing-dev-defs.h
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@@ -240,8 +240,9 @@ static inline void wb_get(struct bdi_writeback *wb)
/**
* wb_put - decrement a wb's refcount
* @wb: bdi_writeback to put
* @nr: number of references to put
*/
static inline void wb_put(struct bdi_writeback *wb)
static inline void wb_put_many(struct bdi_writeback *wb, unsigned long nr)
{
if (WARN_ON_ONCE(!wb->bdi)) {
/*
@@ -252,7 +253,16 @@ static inline void wb_put(struct bdi_writeback *wb)
}
if (wb != &wb->bdi->wb)
percpu_ref_put(&wb->refcnt);
percpu_ref_put_many(&wb->refcnt, nr);
}
/**
* wb_put - decrement a wb's refcount
* @wb: bdi_writeback to put
*/
static inline void wb_put(struct bdi_writeback *wb)
{
wb_put_many(wb, 1);
}
/**
@@ -281,6 +291,10 @@ static inline void wb_put(struct bdi_writeback *wb)
{
}
static inline void wb_put_many(struct bdi_writeback *wb, unsigned long nr)
{
}
static inline bool wb_dying(struct bdi_writeback *wb)
{
return false;