From: Christoph Hellwig <hch@xxxxxx>
This is to avoid the deadlock caused in btrfs because of O_DIRECT |
O_DSYNC.
Filesystems such as btrfs require i_rwsem while performing sync on a
file. iomap_dio_rw() is called under i_rw_sem. This leads to a
deadlock because of:
iomap_dio_complete()
generic_write_sync()
btrfs_sync_file()
Separate out iomap_dio_complete() from iomap_dio_rw(), so filesystems
can call iomap_dio_complete() after unlocking i_rwsem.
Signed-off-by: Goldwyn Rodrigues <rgoldwyn@xxxxxxxx>
---
fs/iomap/direct-io.c | 34 +++++++++++++++++++++++++---------
include/linux/iomap.h | 5 +++++
2 files changed, 30 insertions(+), 9 deletions(-)
diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
index c1aafb2ab990..d970c6bbbe11 100644
--- a/fs/iomap/direct-io.c
+++ b/fs/iomap/direct-io.c
@@ -76,7 +76,7 @@ static void iomap_dio_submit_bio(struct iomap_dio *dio, struct iomap *iomap,
dio->submit.cookie = submit_bio(bio);
}
-static ssize_t iomap_dio_complete(struct iomap_dio *dio)
+ssize_t iomap_dio_complete(struct iomap_dio *dio)
{
const struct iomap_dio_ops *dops = dio->dops;
struct kiocb *iocb = dio->iocb;
@@ -130,6 +130,7 @@ static ssize_t iomap_dio_complete(struct iomap_dio *dio)
return ret;
}
+EXPORT_SYMBOL_GPL(iomap_dio_complete);
static void iomap_dio_complete_work(struct work_struct *work)
{
@@ -406,8 +407,8 @@ iomap_dio_actor(struct inode *inode, loff_t pos, loff_t length,
* Returns -ENOTBLK In case of a page invalidation invalidation failure for
* writes. The callers needs to fall back to buffered I/O in this case.
*/
-ssize_t
-iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
+struct iomap_dio *
+__iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
const struct iomap_ops *ops, const struct iomap_dio_ops *dops,
bool wait_for_completion)
{
@@ -421,14 +422,14 @@ iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
struct iomap_dio *dio;
if (!count)
- return 0;
+ return NULL;
if (WARN_ON(is_sync_kiocb(iocb) && !wait_for_completion))
- return -EIO;
+ return ERR_PTR(-EIO);
dio = kmalloc(sizeof(*dio), GFP_KERNEL);
if (!dio)
- return -ENOMEM;
+ return ERR_PTR(-ENOMEM);
dio->iocb = iocb;
atomic_set(&dio->ref, 1);
@@ -558,7 +559,7 @@ iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
dio->wait_for_completion = wait_for_completion;
if (!atomic_dec_and_test(&dio->ref)) {
if (!wait_for_completion)
- return -EIOCBQUEUED;
+ return ERR_PTR(-EIOCBQUEUED);
for (;;) {
set_current_state(TASK_UNINTERRUPTIBLE);
@@ -574,10 +575,25 @@ iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
__set_current_state(TASK_RUNNING);
}
- return iomap_dio_complete(dio);
+ return dio;
out_free_dio:
kfree(dio);
- return ret;
+ return ERR_PTR(ret);
+}
+EXPORT_SYMBOL_GPL(__iomap_dio_rw);
+
+ssize_t
+iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
+ const struct iomap_ops *ops, const struct iomap_dio_ops *dops,
+ bool wait_for_completion)
+{
+ struct iomap_dio *dio;
+
+ dio = __iomap_dio_rw(iocb, iter, ops, dops, wait_for_completion);
+ if (IS_ERR_OR_NULL(dio))
+ return PTR_ERR_OR_ZERO(dio);
+ return iomap_dio_complete(dio);
}
EXPORT_SYMBOL_GPL(iomap_dio_rw);
+
