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-rw-r--r--fs/iomap.c28
1 files changed, 21 insertions, 7 deletions
diff --git a/fs/iomap.c b/fs/iomap.c
index cb184ff68680..897c60215dd1 100644
--- a/fs/iomap.c
+++ b/fs/iomap.c
@@ -1813,6 +1813,7 @@ iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
loff_t pos = iocb->ki_pos, start = pos;
loff_t end = iocb->ki_pos + count - 1, ret = 0;
unsigned int flags = IOMAP_DIRECT;
+ bool wait_for_completion = is_sync_kiocb(iocb);
struct blk_plug plug;
struct iomap_dio *dio;
@@ -1832,7 +1833,6 @@ iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
dio->end_io = end_io;
dio->error = 0;
dio->flags = 0;
- dio->wait_for_completion = is_sync_kiocb(iocb);
dio->submit.iter = iter;
dio->submit.waiter = current;
@@ -1887,7 +1887,7 @@ iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
dio_warn_stale_pagecache(iocb->ki_filp);
ret = 0;
- if (iov_iter_rw(iter) == WRITE && !dio->wait_for_completion &&
+ if (iov_iter_rw(iter) == WRITE && !wait_for_completion &&
!inode->i_sb->s_dio_done_wq) {
ret = sb_init_dio_done_wq(inode->i_sb);
if (ret < 0)
@@ -1903,7 +1903,7 @@ iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
if (ret <= 0) {
/* magic error code to fall back to buffered I/O */
if (ret == -ENOTBLK) {
- dio->wait_for_completion = true;
+ wait_for_completion = true;
ret = 0;
}
break;
@@ -1925,8 +1925,24 @@ iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
if (dio->flags & IOMAP_DIO_WRITE_FUA)
dio->flags &= ~IOMAP_DIO_NEED_SYNC;
+ /*
+ * We are about to drop our additional submission reference, which
+ * might be the last reference to the dio. There are three three
+ * different ways we can progress here:
+ *
+ * (a) If this is the last reference we will always complete and free
+ * the dio ourselves.
+ * (b) If this is not the last reference, and we serve an asynchronous
+ * iocb, we must never touch the dio after the decrement, the
+ * I/O completion handler will complete and free it.
+ * (c) If this is not the last reference, but we serve a synchronous
+ * iocb, the I/O completion handler will wake us up on the drop
+ * of the final reference, and we will complete and free it here
+ * after we got woken by the I/O completion handler.
+ */
+ dio->wait_for_completion = wait_for_completion;
if (!atomic_dec_and_test(&dio->ref)) {
- if (!dio->wait_for_completion)
+ if (!wait_for_completion)
return -EIOCBQUEUED;
for (;;) {
@@ -1943,9 +1959,7 @@ iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
__set_current_state(TASK_RUNNING);
}
- ret = iomap_dio_complete(dio);
-
- return ret;
+ return iomap_dio_complete(dio);
out_free_dio:
kfree(dio);