summaryrefslogtreecommitdiffstats
path: root/fs/ceph/io.c
diff options
context:
space:
mode:
Diffstat (limited to 'fs/ceph/io.c')
-rw-r--r--fs/ceph/io.c163
1 files changed, 163 insertions, 0 deletions
diff --git a/fs/ceph/io.c b/fs/ceph/io.c
new file mode 100644
index 000000000000..97602ea92ff4
--- /dev/null
+++ b/fs/ceph/io.c
@@ -0,0 +1,163 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2016 Trond Myklebust
+ * Copyright (c) 2019 Jeff Layton
+ *
+ * I/O and data path helper functionality.
+ *
+ * Heavily borrowed from equivalent code in fs/nfs/io.c
+ */
+
+#include <linux/ceph/ceph_debug.h>
+
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/rwsem.h>
+#include <linux/fs.h>
+
+#include "super.h"
+#include "io.h"
+
+/* Call with exclusively locked inode->i_rwsem */
+static void ceph_block_o_direct(struct ceph_inode_info *ci, struct inode *inode)
+{
+ lockdep_assert_held_write(&inode->i_rwsem);
+
+ if (READ_ONCE(ci->i_ceph_flags) & CEPH_I_ODIRECT) {
+ spin_lock(&ci->i_ceph_lock);
+ ci->i_ceph_flags &= ~CEPH_I_ODIRECT;
+ spin_unlock(&ci->i_ceph_lock);
+ inode_dio_wait(inode);
+ }
+}
+
+/**
+ * ceph_start_io_read - declare the file is being used for buffered reads
+ * @inode: file inode
+ *
+ * Declare that a buffered read operation is about to start, and ensure
+ * that we block all direct I/O.
+ * On exit, the function ensures that the CEPH_I_ODIRECT flag is unset,
+ * and holds a shared lock on inode->i_rwsem to ensure that the flag
+ * cannot be changed.
+ * In practice, this means that buffered read operations are allowed to
+ * execute in parallel, thanks to the shared lock, whereas direct I/O
+ * operations need to wait to grab an exclusive lock in order to set
+ * CEPH_I_ODIRECT.
+ * 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
+ceph_start_io_read(struct inode *inode)
+{
+ struct ceph_inode_info *ci = ceph_inode(inode);
+
+ /* Be an optimist! */
+ down_read(&inode->i_rwsem);
+ if (!(READ_ONCE(ci->i_ceph_flags) & CEPH_I_ODIRECT))
+ return;
+ up_read(&inode->i_rwsem);
+ /* Slow path.... */
+ down_write(&inode->i_rwsem);
+ ceph_block_o_direct(ci, inode);
+ downgrade_write(&inode->i_rwsem);
+}
+
+/**
+ * ceph_end_io_read - declare that the buffered read operation is done
+ * @inode: file inode
+ *
+ * Declare that a buffered read operation is done, and release the shared
+ * lock on inode->i_rwsem.
+ */
+void
+ceph_end_io_read(struct inode *inode)
+{
+ up_read(&inode->i_rwsem);
+}
+
+/**
+ * ceph_start_io_write - declare the file is being used for buffered writes
+ * @inode: file inode
+ *
+ * Declare that a buffered write operation is about to start, and ensure
+ * that we block all direct I/O.
+ */
+void
+ceph_start_io_write(struct inode *inode)
+{
+ down_write(&inode->i_rwsem);
+ ceph_block_o_direct(ceph_inode(inode), inode);
+}
+
+/**
+ * ceph_end_io_write - declare that the buffered write operation is done
+ * @inode: file inode
+ *
+ * Declare that a buffered write operation is done, and release the
+ * lock on inode->i_rwsem.
+ */
+void
+ceph_end_io_write(struct inode *inode)
+{
+ up_write(&inode->i_rwsem);
+}
+
+/* Call with exclusively locked inode->i_rwsem */
+static void ceph_block_buffered(struct ceph_inode_info *ci, struct inode *inode)
+{
+ lockdep_assert_held_write(&inode->i_rwsem);
+
+ if (!(READ_ONCE(ci->i_ceph_flags) & CEPH_I_ODIRECT)) {
+ spin_lock(&ci->i_ceph_lock);
+ ci->i_ceph_flags |= CEPH_I_ODIRECT;
+ spin_unlock(&ci->i_ceph_lock);
+ /* FIXME: unmap_mapping_range? */
+ filemap_write_and_wait(inode->i_mapping);
+ }
+}
+
+/**
+ * ceph_end_io_direct - declare the file is being used for direct i/o
+ * @inode: file inode
+ *
+ * Declare that a direct I/O operation is about to start, and ensure
+ * that we block all buffered I/O.
+ * On exit, the function ensures that the CEPH_I_ODIRECT flag is set,
+ * and holds a shared lock on inode->i_rwsem to ensure that the flag
+ * cannot be changed.
+ * In practice, this means that direct I/O operations are allowed to
+ * execute in parallel, thanks to the shared lock, whereas buffered I/O
+ * operations need to wait to grab an exclusive lock in order to clear
+ * CEPH_I_ODIRECT.
+ * 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
+ceph_start_io_direct(struct inode *inode)
+{
+ struct ceph_inode_info *ci = ceph_inode(inode);
+
+ /* Be an optimist! */
+ down_read(&inode->i_rwsem);
+ if (READ_ONCE(ci->i_ceph_flags) & CEPH_I_ODIRECT)
+ return;
+ up_read(&inode->i_rwsem);
+ /* Slow path.... */
+ down_write(&inode->i_rwsem);
+ ceph_block_buffered(ci, inode);
+ downgrade_write(&inode->i_rwsem);
+}
+
+/**
+ * ceph_end_io_direct - declare that the direct i/o operation is done
+ * @inode: file inode
+ *
+ * Declare that a direct I/O operation is done, and release the shared
+ * lock on inode->i_rwsem.
+ */
+void
+ceph_end_io_direct(struct inode *inode)
+{
+ up_read(&inode->i_rwsem);
+}