linux-ext4 - [PATCH 2/3] ext4: fix inode rwsem regression

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Date:   Wed, 11 Sep 2019 11:45:16 -0500
From:   Goldwyn Rodrigues <rgoldwyn@...e.de>
To:     linux-fsdevel@...r.kernel.org
Cc:     linux-ext4@...r.kernel.org, linux-btrfs@...r.kernel.org,
        hch@...radead.org, andres@...razel.de, david@...morbit.com,
        riteshh@...ux.ibm.com, linux-f2fs-devel@...ts.sourceforge.net,
        Goldwyn Rodrigues <rgoldwyn@...e.com>
Subject: [PATCH 2/3] ext4: fix inode rwsem regression

From: Goldwyn Rodrigues <rgoldwyn@...e.com>

This is similar to 942491c9e6d6 ("xfs: fix AIM7 regression")
Apparently our current rwsem code doesn't like doing the trylock, then
lock for real scheme.  So change our read/write methods to just do the
trylock for the RWF_NOWAIT case.

Fixes: 728fbc0e10b7 ("ext4: nowait aio support")
Signed-off-by: Goldwyn Rodrigues <rgoldwyn@...e.com>
---
 fs/ext4/file.c | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index 70b0438dbc94..d5b2d0cc325d 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -40,11 +40,13 @@ static ssize_t ext4_dax_read_iter(struct kiocb *iocb, struct iov_iter *to)
 	struct inode *inode = file_inode(iocb->ki_filp);
 	ssize_t ret;
 
-	if (!inode_trylock_shared(inode)) {
-		if (iocb->ki_flags & IOCB_NOWAIT)
+	if (iocb->ki_flags & IOCB_NOWAIT) {
+		if (!inode_trylock_shared(inode))
 			return -EAGAIN;
+	} else {
 		inode_lock_shared(inode);
 	}
+
 	/*
 	 * Recheck under inode lock - at this point we are sure it cannot
 	 * change anymore
@@ -190,11 +192,13 @@ ext4_dax_write_iter(struct kiocb *iocb, struct iov_iter *from)
 	struct inode *inode = file_inode(iocb->ki_filp);
 	ssize_t ret;
 
-	if (!inode_trylock(inode)) {
-		if (iocb->ki_flags & IOCB_NOWAIT)
+	if (iocb->ki_flags & IOCB_NOWAIT) {
+		if (!inode_trylock(inode))
 			return -EAGAIN;
+	} else {
 		inode_lock(inode);
 	}
+
 	ret = ext4_write_checks(iocb, from);
 	if (ret <= 0)
 		goto out;
@@ -233,9 +237,10 @@ ext4_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
 	if (!o_direct && (iocb->ki_flags & IOCB_NOWAIT))
 		return -EOPNOTSUPP;
 
-	if (!inode_trylock(inode)) {
-		if (iocb->ki_flags & IOCB_NOWAIT)
+	if (iocb->ki_flags & IOCB_NOWAIT) {
+		if (!inode_trylock(inode))
 			return -EAGAIN;
+	} else {
 		inode_lock(inode);
 	}
 
-- 
2.16.4