fs/nfs/io: make nfs_start_io_*() killable

This allows killing processes that wait for a lock when one process is
stuck waiting for the NFS server.  This aims to complete the coverage
of NFS operations being killable, like nfs_direct_wait() does, for
example.

Signed-off-by: Max Kellermann <[email protected]>
Signed-off-by: Trond Myklebust <[email protected]>

1 files changed, 33 insertions, 11 deletions

diff --git a/fs/nfs/io.c b/fs/nfs/io.c
index b5551ed8f648..3388faf2acb9 100644
--- a/fs/nfs/io.c
+++ b/fs/nfs/io.c
@@ -39,19 +39,28 @@ static void nfs_block_o_direct(struct nfs_inode *nfsi, struct inode *inode)
  * Note that buffered writes and truncates both take a write lock on
  * inode->i_rwsem, meaning that those are serialised w.r.t. the reads.
  */
-void
+int
 nfs_start_io_read(struct inode *inode)
 {
 	struct nfs_inode *nfsi = NFS_I(inode);
+	int err;
+
 	/* Be an optimist! */
-	down_read(&inode->i_rwsem);
+	err = down_read_killable(&inode->i_rwsem);
+	if (err)
+		return err;
 	if (test_bit(NFS_INO_ODIRECT, &nfsi->flags) == 0)
-		return;
+		return 0;
 	up_read(&inode->i_rwsem);
+
 	/* Slow path.... */
-	down_write(&inode->i_rwsem);
+	err = down_write_killable(&inode->i_rwsem);
+	if (err)
+		return err;
 	nfs_block_o_direct(nfsi, inode);
 	downgrade_write(&inode->i_rwsem);
+
+	return 0;
 }
 
 /**
@@ -74,11 +83,15 @@ nfs_end_io_read(struct inode *inode)
  * Declare that a buffered read operation is about to start, and ensure
  * that we block all direct I/O.
  */
-void
+int
 nfs_start_io_write(struct inode *inode)
 {
-	down_write(&inode->i_rwsem);
-	nfs_block_o_direct(NFS_I(inode), inode);
+	int err;
+
+	err = down_write_killable(&inode->i_rwsem);
+	if (!err)
+		nfs_block_o_direct(NFS_I(inode), inode);
+	return err;
 }
 
 /**
@@ -119,19 +132,28 @@ static void nfs_block_buffered(struct nfs_inode *nfsi, struct inode *inode)
  * Note that buffered writes and truncates both take a write lock on
  * inode->i_rwsem, meaning that those are serialised w.r.t. O_DIRECT.
  */
-void
+int
 nfs_start_io_direct(struct inode *inode)
 {
 	struct nfs_inode *nfsi = NFS_I(inode);
+	int err;
+
 	/* Be an optimist! */
-	down_read(&inode->i_rwsem);
+	err = down_read_killable(&inode->i_rwsem);
+	if (err)
+		return err;
 	if (test_bit(NFS_INO_ODIRECT, &nfsi->flags) != 0)
-		return;
+		return 0;
 	up_read(&inode->i_rwsem);
+
 	/* Slow path.... */
-	down_write(&inode->i_rwsem);
+	err = down_write_killable(&inode->i_rwsem);
+	if (err)
+		return err;
 	nfs_block_buffered(nfsi, inode);
 	downgrade_write(&inode->i_rwsem);
+
+	return 0;
 }
 
 /**