| Message ID | 154542108460.3682905.4453912339454331429.stgit@dwillia2-desk3.amr.corp.intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | dax: Use non-exclusive wait in wait_entry_unlocked() | expand |
On Fri 21-12-18 11:38:04, Dan Williams wrote: > 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> > --- > fs/dax.c | 16 +++++++--------- > 1 file changed, 7 insertions(+), 9 deletions(-) Thanks for cleaning this up! The patch looks good to me. You can add: Reviewed-by: Jan Kara <jack@suse.cz> Honza > > diff --git a/fs/dax.c b/fs/dax.c > index 48132eca3761..042d3b31b413 100644 > --- a/fs/dax.c > +++ b/fs/dax.c > @@ -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) >
diff --git a/fs/dax.c b/fs/dax.c index 48132eca3761..042d3b31b413 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -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)
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> --- fs/dax.c | 16 +++++++--------- 1 file changed, 7 insertions(+), 9 deletions(-)