On Wed, Nov 28, 2018 at 3:54 AM Jan Kara jack@suse.cz wrote:
On Tue 27-11-18 13:16:34, Matthew Wilcox wrote:
After we drop the i_pages lock, the inode can be freed at any time. The get_unlocked_entry() code has no choice but to reacquire the lock, so it can't be used here. Create a new wait_entry_unlocked() which takes care not to acquire the lock or dereference the address_space in any way.
Fixes: c2a7d2a11552 ("filesystem-dax: Introduce dax_lock_mapping_entry()") Cc: stable@vger.kernel.org Signed-off-by: Matthew Wilcox willy@infradead.org
The patch looks good. You can add:
Reviewed-by: Jan Kara jack@suse.cz
Just one nit below:
+/*
- The only thing keeping the address space around is the i_pages lock
- (it's cycled in clear_inode() after removing the entries from i_pages)
- After we call xas_unlock_irq(), we cannot touch xas->xa.
- */
+static void wait_entry_unlocked(struct xa_state *xas, void *entry) +{
struct wait_exceptional_entry_queue ewait;wait_queue_head_t *wq;init_wait(&ewait.wait);ewait.wait.func = wake_exceptional_entry_func;wq = dax_entry_waitqueue(xas, entry, &ewait.key);prepare_to_wait_exclusive(wq, &ewait.wait, TASK_UNINTERRUPTIBLE);xas_unlock_irq(xas);schedule();finish_wait(wq, &ewait.wait);Can we add a comment here like:
/* * Entry lock waits are exclusive. Wake up the next waiter since we * aren't sure we will acquire the entry lock and thus wake the * next waiter up on unlock. */Because I always wonder for a moment why this is needed.
Looks good, I'll add that when applying.