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| author | Tejun Heo <tj@kernel.org> | 2016-02-29 18:28:53 -0500 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2016-03-09 15:34:52 -0800 |
| commit | c5cbbec54fe71c4de2d34f8c0ec8fbfdd7f17339 (patch) | |
| tree | 4fff87c2a948702a0b3ea9144ba221064f182620 /include/linux | |
| parent | 7adb5cc0f39be29c16fae035d9e30e332095bbbc (diff) | |
| download | lwn-c5cbbec54fe71c4de2d34f8c0ec8fbfdd7f17339.tar.gz lwn-c5cbbec54fe71c4de2d34f8c0ec8fbfdd7f17339.zip | |
writeback: flush inode cgroup wb switches instead of pinning super_block
commit a1a0e23e49037c23ea84bc8cc146a03584d13577 upstream.
If cgroup writeback is in use, inodes can be scheduled for
asynchronous wb switching. Before 5ff8eaac1636 ("writeback: keep
superblock pinned during cgroup writeback association switches"), this
could race with umount leading to super_block being destroyed while
inodes are pinned for wb switching. 5ff8eaac1636 fixed it by bumping
s_active while wb switches are in flight; however, this allowed
in-flight wb switches to make umounts asynchronous when the userland
expected synchronosity - e.g. fsck immediately following umount may
fail because the device is still busy.
This patch removes the problematic super_block pinning and instead
makes generic_shutdown_super() flush in-flight wb switches. wb
switches are now executed on a dedicated isw_wq so that they can be
flushed and isw_nr_in_flight keeps track of the number of in-flight wb
switches so that flushing can be avoided in most cases.
v2: Move cgroup_writeback_umount() further below and add MS_ACTIVE
check in inode_switch_wbs() as Jan an Al suggested.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Tahsin Erdogan <tahsin@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Link: http://lkml.kernel.org/g/CAAeU0aNCq7LGODvVGRU-oU_o-6enii5ey0p1c26D1ZzYwkDc5A@mail.gmail.com
Fixes: 5ff8eaac1636 ("writeback: keep superblock pinned during cgroup writeback association switches")
Reviewed-by: Jan Kara <jack@suse.cz>
Tested-by: Tahsin Erdogan <tahsin@google.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'include/linux')
| -rw-r--r-- | include/linux/writeback.h | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/include/linux/writeback.h b/include/linux/writeback.h index b333c945e571..d0b5ca5d4e08 100644 --- a/include/linux/writeback.h +++ b/include/linux/writeback.h @@ -198,6 +198,7 @@ void wbc_attach_and_unlock_inode(struct writeback_control *wbc, void wbc_detach_inode(struct writeback_control *wbc); void wbc_account_io(struct writeback_control *wbc, struct page *page, size_t bytes); +void cgroup_writeback_umount(void); /** * inode_attach_wb - associate an inode with its wb @@ -301,6 +302,10 @@ static inline void wbc_account_io(struct writeback_control *wbc, { } +static inline void cgroup_writeback_umount(void) +{ +} + #endif /* CONFIG_CGROUP_WRITEBACK */ /* |