From c3d4ed1abecfcfc801199cfadb71f5b80e025d9e Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Mon, 28 Sep 2020 08:51:08 -0700 Subject: [PATCH] iomap: Allow filesystem to call iomap_dio_complete without i_rwsem 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: Christoph Hellwig Reviewed-by: Josef Bacik Signed-off-by: Goldwyn Rodrigues Reviewed-by: Darrick J. Wong Signed-off-by: Darrick J. Wong --- fs/iomap/direct-io.c | 35 ++++++++++++++++++++++++++--------- include/linux/iomap.h | 5 +++++ 2 files changed, 31 insertions(+), 9 deletions(-) diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c index 024d4bb3028e..b005ef5f554e 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) { @@ -416,8 +417,8 @@ 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) { @@ -431,14 +432,14 @@ 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); @@ -568,7 +569,7 @@ 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); @@ -584,10 +585,26 @@ 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; + if (ret) + return ERR_PTR(ret); + return NULL; +} +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); diff --git a/include/linux/iomap.h b/include/linux/iomap.h index 4d1d3c3469e9..172b3397a1a3 100644 --- a/include/linux/iomap.h +++ b/include/linux/iomap.h @@ -13,6 +13,7 @@ struct address_space; struct fiemap_extent_info; struct inode; +struct iomap_dio; struct iomap_writepage_ctx; struct iov_iter; struct kiocb; @@ -258,6 +259,10 @@ struct iomap_dio_ops { 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 *__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); +ssize_t iomap_dio_complete(struct iomap_dio *dio); int iomap_dio_iopoll(struct kiocb *kiocb, bool spin); #ifdef CONFIG_SWAP -- 2.20.1