[PATCH 4/8] btrfs: Introduce btrfs_inode_lock()/unlock()

[Goldwyn Rodrigues <rgoldwyn@xxxxxxx>]

From: Goldwyn Rodrigues <rgoldwyn@xxxxxxxx>

btrfs_inode_lock/unlock() acquires the inode->i_rwsem depending on the
flags passed. ilock_flags determines the type of lock to be taken:

BTRFS_ILOCK_SHARED - for shared locks, for possible parallel DIO
BTRFS_ILOCK_TRY - for the RWF_NOWAIT sequence

Signed-off-by: Goldwyn Rodrigues <rgoldwyn@xxxxxxxx>
---
 fs/btrfs/ctree.h |  8 ++++++++
 fs/btrfs/file.c  | 51 +++++++++++++++++++++++++++++++++++++++---------
 2 files changed, 50 insertions(+), 9 deletions(-)

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 161533040978..346fea668ca0 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -2953,6 +2953,14 @@ void btrfs_update_ioctl_balance_args(struct btrfs_fs_info *fs_info,
 			       struct btrfs_ioctl_balance_args *bargs);
 
 /* file.c */
+
+/* ilock flags definition */
+#define BTRFS_ILOCK_SHARED	0x1
+#define BTRFS_ILOCK_TRY 	0x2
+
+int btrfs_inode_lock(struct inode *inode, int ilock_flags);
+void btrfs_inode_unlock(struct inode *inode, int ilock_flags);
+
 int __init btrfs_auto_defrag_init(void);
 void __cold btrfs_auto_defrag_exit(void);
 int btrfs_add_inode_defrag(struct btrfs_trans_handle *trans,
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index ba7c3b2cf1c5..1a9a0a9e4b3d 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -70,6 +70,37 @@ static int __compare_inode_defrag(struct inode_defrag *defrag1,
 		return 0;
 }
 
+int btrfs_inode_lock(struct inode *inode, int ilock_flags)
+{
+	if (ilock_flags & BTRFS_ILOCK_SHARED) {
+		if (ilock_flags & BTRFS_ILOCK_TRY) {
+			if (!inode_trylock_shared(inode))
+				return -EAGAIN;
+			else
+				return 0;
+		}
+		inode_lock_shared(inode);
+	} else {
+		if (ilock_flags & BTRFS_ILOCK_TRY) {
+			if (!inode_trylock(inode))
+				return -EAGAIN;
+			else
+				return 0;
+		}
+		inode_lock(inode);
+	}
+	return 0;
+}
+
+void btrfs_inode_unlock(struct inode *inode, int ilock_flags)
+{
+	if (ilock_flags & BTRFS_ILOCK_SHARED)
+		inode_unlock_shared(inode);
+	else
+		inode_unlock(inode);
+
+}
+
 /* pop a record for an inode into the defrag tree.  The lock
  * must be held already
  *
@@ -1978,6 +2009,7 @@ static ssize_t btrfs_file_write_iter(struct kiocb *iocb,
 	ssize_t num_written = 0;
 	const bool sync = iocb->ki_flags & IOCB_DSYNC;
 	ssize_t err;
+	int ilock_flags = 0;
 
 	/*
 	 * If BTRFS flips readonly due to some impossible error
@@ -1992,12 +2024,12 @@ static ssize_t btrfs_file_write_iter(struct kiocb *iocb,
 	    (iocb->ki_flags & IOCB_NOWAIT))
 		return -EOPNOTSUPP;
 
-	if (iocb->ki_flags & IOCB_NOWAIT) {
-		if (!inode_trylock(inode))
-			return -EAGAIN;
-	} else {
-		inode_lock(inode);
-	}
+	if (iocb->ki_flags & IOCB_NOWAIT)
+		ilock_flags |= BTRFS_ILOCK_TRY;
+
+	err = btrfs_inode_lock(inode, ilock_flags);
+	if (err < 0)
+		goto out;
 
 	err = btrfs_write_check(iocb, from);
 	if (err <= 0) {
@@ -2014,7 +2046,7 @@ static ssize_t btrfs_file_write_iter(struct kiocb *iocb,
 		num_written = btrfs_buffered_write(iocb, from);
 	}
 
-	inode_unlock(inode);
+	btrfs_inode_unlock(inode, ilock_flags);
 
 	/*
 	 * We also have to set last_sub_trans to the current log transid,
@@ -3547,9 +3579,10 @@ static ssize_t btrfs_direct_read(struct kiocb *iocb, struct iov_iter *to)
 	if (is_sync_kiocb(iocb))
 		flags |= IOMAP_DIOF_WAIT_FOR_COMPLETION;
 
-	inode_lock_shared(inode);
+	btrfs_inode_lock(inode, BTRFS_ILOCK_SHARED);
         ret = iomap_dio_rw(iocb, to, &btrfs_dio_iomap_ops, &btrfs_dops, flags);
-	inode_unlock_shared(inode);
+	btrfs_inode_unlock(inode, BTRFS_ILOCK_SHARED);
+
 	return ret;
 }
 
-- 
2.25.0