The patch titled
dio: remove duplicate bio wait code
has been added to the -mm tree. Its filename is
dio-remove-duplicate-bio-wait-code.patch
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: dio: remove duplicate bio wait code
From: Zach Brown <zach.brown@xxxxxxxxxx>
Now that we have a single refcount and waiting path we can reuse it in the
async 'should_wait' path. It continues to rely on the fragile link between
the conditional in dio_complete_aio() which decides to complete the AIO and
the conditional in direct_io_worker() which decides to wait and free.
By waiting before dropping the reference we stop dio_bio_end_aio() from
calling dio_complete_aio() which used to wake up the waiter after seeing the
reference count drop to 0. We hoist this wake up into dio_bio_end_aio() which
now notices when it's left a single remaining reference that is held by the
waiter.
Signed-off-by: Zach Brown <zach.brown@xxxxxxxxxx>
Cc: Badari Pulavarty <pbadari@xxxxxxxxxx>
Cc: Suparna Bhattacharya <suparna@xxxxxxxxxx>
Acked-by: Jeff Moyer <jmoyer@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---
fs/direct-io.c | 41 ++++++++++++-----------------------------
1 files changed, 12 insertions(+), 29 deletions(-)
diff -puN fs/direct-io.c~dio-remove-duplicate-bio-wait-code fs/direct-io.c
--- a/fs/direct-io.c~dio-remove-duplicate-bio-wait-code
+++ a/fs/direct-io.c
@@ -256,7 +256,6 @@ static int dio_complete(struct dio *dio,
*/
static void dio_complete_aio(struct dio *dio)
{
- unsigned long flags;
int ret;
ret = dio_complete(dio, dio->iocb->ki_pos, 0);
@@ -266,14 +265,6 @@ static void dio_complete_aio(struct dio
((dio->rw == READ) && dio->result)) {
aio_complete(dio->iocb, ret, 0);
kfree(dio);
- } else {
- /*
- * Falling back to buffered
- */
- spin_lock_irqsave(&dio->bio_lock, flags);
- if (dio->waiter)
- wake_up_process(dio->waiter);
- spin_unlock_irqrestore(&dio->bio_lock, flags);
}
}
@@ -284,6 +275,8 @@ static int dio_bio_complete(struct dio *
static int dio_bio_end_aio(struct bio *bio, unsigned int bytes_done, int error)
{
struct dio *dio = bio->bi_private;
+ int waiter_holds_ref = 0;
+ int remaining;
if (bio->bi_size)
return 1;
@@ -291,7 +284,12 @@ static int dio_bio_end_aio(struct bio *b
/* cleanup the bio */
dio_bio_complete(dio, bio);
- if (atomic_dec_and_test(&dio->refcount))
+ waiter_holds_ref = !!dio->waiter;
+ remaining = atomic_sub_return(1, (&dio->refcount));
+ if (remaining == 1 && waiter_holds_ref)
+ wake_up_process(dio->waiter);
+
+ if (remaining == 0)
dio_complete_aio(dio);
return 0;
@@ -1089,30 +1087,15 @@ direct_io_worker(int rw, struct kiocb *i
if (ret == 0)
ret = dio->result;
+ if (should_wait)
+ dio_await_completion(dio);
+
/* this can free the dio */
if (atomic_dec_and_test(&dio->refcount))
dio_complete_aio(dio);
- if (should_wait) {
- unsigned long flags;
- /*
- * Wait for already issued I/O to drain out and
- * release its references to user-space pages
- * before returning to fallback on buffered I/O
- */
-
- spin_lock_irqsave(&dio->bio_lock, flags);
- set_current_state(TASK_UNINTERRUPTIBLE);
- while (atomic_read(&dio->refcount)) {
- spin_unlock_irqrestore(&dio->bio_lock, flags);
- io_schedule();
- spin_lock_irqsave(&dio->bio_lock, flags);
- set_current_state(TASK_UNINTERRUPTIBLE);
- }
- spin_unlock_irqrestore(&dio->bio_lock, flags);
- set_current_state(TASK_RUNNING);
+ if (should_wait)
kfree(dio);
- }
} else {
dio_await_completion(dio);
_
Patches currently in -mm which might be from zach.brown@xxxxxxxxxx are
origin.patch
pr_debug-aio-use-size_t-length-modifier-in-pr_debug-format-arguments.patch
pr_debug-configfs-use-size_t-length-modifier-in-pr_debug-format-argument.patch
pr_debug-sysfs-use-size_t-length-modifier-in-pr_debug-format-arguments.patch
pr_debug-umem-repair-nonexistant-bh-pr_debug-reference.patch
pr_debug-tipar-repair-nonexistant-pr_debug-argument-use.patch
pr_debug-dell_rbu-fix-pr_debug-argument-warnings.patch
pr_debug-ifb-replace-missing-comma-to-separate-pr_debug-arguments.patch
pr_debug-trident-use-size_t-length-modifier-in-pr_debug-format-arguments.patch
pr_debug-check-pr_debug-arguments-arm-fix.patch
isdn-debug-build-fix.patch
isdn-more-pr_debug-fixes.patch
pr_debug-check-pr_debug-arguments.patch
dio-centralize-completion-in-dio_complete.patch
dio-call-blk_run_address_space-once-per-op.patch
dio-formalize-bio-counters-as-a-dio-reference-count.patch
dio-remove-duplicate-bio-wait-code.patch
dio-only-call-aio_complete-after-returning-eiocbqueued.patch
-
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