| From | Ben Hutchings <> | Date | Wed, 24 Jul 2013 15:02:45 +0100 | Subject | [50/85] writeback: Fix periodic writeback after fs mount |
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3.2.49-rc1 review patch. If anyone has any objections, please let me know.
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From: Jan Kara <jack@suse.cz>
commit a5faeaf9109578e65e1a32e2a3e76c8b47e7dcb6 upstream.
Code in blkdev.c moves a device inode to default_backing_dev_info when the last reference to the device is put and moves the device inode back to its bdi when the first reference is acquired. This includes moving to wb.b_dirty list if the device inode is dirty. The code however doesn't setup timer to wake corresponding flusher thread and while wb.b_dirty list is non-empty __mark_inode_dirty() will not set it up either. Thus periodic writeback is effectively disabled until a sync(2) call which can lead to unexpected data loss in case of crash or power failure.
Fix the problem by setting up a timer for periodic writeback in case we add the first dirty inode to wb.b_dirty list in bdev_inode_switch_bdi().
Reported-by: Bert De Jonghe <Bert.DeJonghe@amplidata.com> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Ben Hutchings <ben@decadent.org.uk> --- fs/block_dev.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-)
--- a/fs/block_dev.c +++ b/fs/block_dev.c @@ -55,17 +55,24 @@ static void bdev_inode_switch_bdi(struct struct backing_dev_info *dst) { struct backing_dev_info *old = inode->i_data.backing_dev_info; + bool wakeup_bdi = false; if (unlikely(dst == old)) /* deadlock avoidance */ return; bdi_lock_two(&old->wb, &dst->wb); spin_lock(&inode->i_lock); inode->i_data.backing_dev_info = dst; - if (inode->i_state & I_DIRTY) + if (inode->i_state & I_DIRTY) { + if (bdi_cap_writeback_dirty(dst) && !wb_has_dirty_io(&dst->wb)) + wakeup_bdi = true; list_move(&inode->i_wb_list, &dst->wb.b_dirty); + } spin_unlock(&inode->i_lock); spin_unlock(&old->wb.list_lock); spin_unlock(&dst->wb.list_lock); + + if (wakeup_bdi) + bdi_wakeup_thread_delayed(dst); } sector_t blkdev_max_block(struct block_device *bdev)
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