This patch fixes a hard-to-trigger condition, where the inode is on the
inode_in_use list while it's state is dirty. In this state dirty pages are
not written back in sync() or from kupdate, only from direct page reclaim.
And this causes a livelock in balance_dirty_pages after a while.
The actual sequence of events required to get into this state is:
thread function inode state inode list
----------------------------------------------------------------------------
1 __sync_single_inode (background) I_DIRTY sb->s_io
1 do_writepages ... I_LOCKED
2 __writeback_single_inode (sync) sleeps I_LOCKED
1 __sync_single_inode (background) finish 0 inode_in_use
2 __writeback_single_inode (sync) wakeup 0
2 __sync_single_inode (sync) 0
2 do_writepages ... I_LOCKED
3 __mark_inode_dirty I_LOCKED | I_DIRTY
2 __sync_single_inode (sync) finish I_DIRTY left on
inode_in_use
Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
} else if (inode->i_state & I_DIRTY) {
/*
* Someone redirtied the inode while were writing back
- * the pages: nothing to do.
+ * the pages.
*/
+ list_move(&inode->i_list, &sb->s_dirty);
} else if (atomic_read(&inode->i_count)) {
/*
* The inode is clean, inuse