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dax: Use non-exclusive wait in wait_entry_unlocked() 

get_unlocked_entry() uses an exclusive wait because it is guaranteed to
eventually obtain the lock and follow on with an unlock+wakeup cycle.
The wait_entry_unlocked() path does not have the same guarantee. Rather
than open-code an extra wakeup, just switch to a non-exclusive wait.

Cc: Jan Kara <jack@suse.cz>
Cc: Matthew Wilcox <willy@infradead.org>
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
hifive-unleashed-5.1
Dan Williams 2018-12-21 11:35:53 -08:00
parent 7566ec393f
commit d8a706414a
1 changed files with 7 additions and 9 deletions
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16
fs/dax.c
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@ -246,18 +246,16 @@ static void wait_entry_unlocked(struct xa_state *xas, void *entry)
ewait.wait.func = wake_exceptional_entry_func;
wq = dax_entry_waitqueue(xas, entry, &ewait.key);
prepare_to_wait_exclusive(wq, &ewait.wait, TASK_UNINTERRUPTIBLE);
/*
* Unlike get_unlocked_entry() there is no guarantee that this
* path ever successfully retrieves an unlocked entry before an
* inode dies. Perform a non-exclusive wait in case this path
* never successfully performs its own wake up.
*/
prepare_to_wait(wq, &ewait.wait, TASK_UNINTERRUPTIBLE);
xas_unlock_irq(xas);
schedule();
finish_wait(wq, &ewait.wait);
/*
* 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.
*/
if (waitqueue_active(wq))
__wake_up(wq, TASK_NORMAL, 1, &ewait.key);
}
static void put_unlocked_entry(struct xa_state *xas, void *entry)