[PATCH 8/8] btrfs: remove BTRFS_INODE_READDIO_NEED_LOCK

From: Goldwyn Rodrigues <rgoldwyn@suse.de>
To: linux-btrfs@vger.kernel.org
Cc: hch@infradead.org, darrick.wong@oracle.com, fdmanana@kernel.org,
	nborisov@suse.com, dsterba@suse.cz, jthumshirn@suse.de,
	linux-fsdevel@vger.kernel.org,
	Goldwyn Rodrigues <rgoldwyn@suse.com>
Subject: [PATCH 8/8] btrfs: remove BTRFS_INODE_READDIO_NEED_LOCK
Date: Tue, 10 Dec 2019 17:01:55 -0600	[thread overview]
Message-ID: <20191210230155.22688-9-rgoldwyn@suse.de> (raw)
In-Reply-To: <20191210230155.22688-1-rgoldwyn@suse.de>

From: Goldwyn Rodrigues <rgoldwyn@suse.com>

Since we now perform direct reads using i_rwsem, we can remove this
inode flag used to co-ordinate unlocked reads.

The truncate call chain gets the i_rwsem which may conflict with direct
reads:
do_truncate <-- calls inode_lock
  notify_change
   ->setattr/btrfs_setattr
     btrfs_setsize

Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
---
 fs/btrfs/btrfs_inode.h | 18 ------------------
 fs/btrfs/inode.c       |  5 -----
 2 files changed, 23 deletions(-)

diff --git a/fs/btrfs/btrfs_inode.h b/fs/btrfs/btrfs_inode.h
index 4e12a477d32e..cd8f378ed8e7 100644
--- a/fs/btrfs/btrfs_inode.h
+++ b/fs/btrfs/btrfs_inode.h
@@ -27,7 +27,6 @@ enum {
 	BTRFS_INODE_NEEDS_FULL_SYNC,
 	BTRFS_INODE_COPY_EVERYTHING,
 	BTRFS_INODE_IN_DELALLOC_LIST,
-	BTRFS_INODE_READDIO_NEED_LOCK,
 	BTRFS_INODE_HAS_PROPS,
 	BTRFS_INODE_SNAPSHOT_FLUSH,
 };
@@ -317,23 +316,6 @@ struct btrfs_dio_private {
 			blk_status_t);
 };
 
-/*
- * Disable DIO read nolock optimization, so new dio readers will be forced
- * to grab i_mutex. It is used to avoid the endless truncate due to
- * nonlocked dio read.
- */
-static inline void btrfs_inode_block_unlocked_dio(struct btrfs_inode *inode)
-{
-	set_bit(BTRFS_INODE_READDIO_NEED_LOCK, &inode->runtime_flags);
-	smp_mb();
-}
-
-static inline void btrfs_inode_resume_unlocked_dio(struct btrfs_inode *inode)
-{
-	smp_mb__before_atomic();
-	clear_bit(BTRFS_INODE_READDIO_NEED_LOCK, &inode->runtime_flags);
-}
-
 /* Array of bytes with variable length, hexadecimal format 0x1234 */
 #define CSUM_FMT				"0x%*phN"
 #define CSUM_FMT_VALUE(size, bytes)		size, bytes
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index ce53f2889673..4c76a6d5e6a4 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -5273,11 +5273,6 @@ static int btrfs_setsize(struct inode *inode, struct iattr *attr)
 
 		truncate_setsize(inode, newsize);
 
-		/* Disable nonlocked read DIO to avoid the endless truncate */
-		btrfs_inode_block_unlocked_dio(BTRFS_I(inode));
-		inode_dio_wait(inode);
-		btrfs_inode_resume_unlocked_dio(BTRFS_I(inode));
-
 		ret = btrfs_truncate(inode, newsize == oldsize);
 		if (ret && inode->i_nlink) {
 			int err;
-- 
2.16.4

