1 files changed, 104 insertions, 0 deletions
diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
new file mode 100644
index 000000000000..f7a1390d67f5
--- /dev/null
+++ b/include/linux/backing-dev.h
@@ -0,0 +1,104 @@
+/*
+ * include/linux/backing-dev.h
+ *
+ * low-level device information and state which is propagated up through
+ * to high-level code.
+ */
+
+#ifndef _LINUX_BACKING_DEV_H
+#define _LINUX_BACKING_DEV_H
+
+#include <asm/atomic.h>
+
+/*
+ * Bits in backing_dev_info.state
+ */
+enum bdi_state {
+	BDI_pdflush,		/* A pdflush thread is working this device */
+	BDI_write_congested,	/* The write queue is getting full */
+	BDI_read_congested,	/* The read queue is getting full */
+	BDI_unused,		/* Available bits start here */
+};
+
+typedef int (congested_fn)(void *, int);
+
+struct backing_dev_info {
+	unsigned long ra_pages;	/* max readahead in PAGE_CACHE_SIZE units */
+	unsigned long state;	/* Always use atomic bitops on this */
+	unsigned int capabilities; /* Device capabilities */
+	congested_fn *congested_fn; /* Function pointer if device is md/dm */
+	void *congested_data;	/* Pointer to aux data for congested func */
+	void (*unplug_io_fn)(struct backing_dev_info *, struct page *);
+	void *unplug_io_data;
+};
+
+
+/*
+ * Flags in backing_dev_info::capability
+ * - The first two flags control whether dirty pages will contribute to the
+ *   VM's accounting and whether writepages() should be called for dirty pages
+ *   (something that would not, for example, be appropriate for ramfs)
+ * - These flags let !MMU mmap() govern direct device mapping vs immediate
+ *   copying more easily for MAP_PRIVATE, especially for ROM filesystems
+ */
+#define BDI_CAP_NO_ACCT_DIRTY	0x00000001	/* Dirty pages shouldn't contribute to accounting */
+#define BDI_CAP_NO_WRITEBACK	0x00000002	/* Don't write pages back */
+#define BDI_CAP_MAP_COPY	0x00000004	/* Copy can be mapped (MAP_PRIVATE) */
+#define BDI_CAP_MAP_DIRECT	0x00000008	/* Can be mapped directly (MAP_SHARED) */
+#define BDI_CAP_READ_MAP	0x00000010	/* Can be mapped for reading */
+#define BDI_CAP_WRITE_MAP	0x00000020	/* Can be mapped for writing */
+#define BDI_CAP_EXEC_MAP	0x00000040	/* Can be mapped for execution */
+#define BDI_CAP_VMFLAGS \
+	(BDI_CAP_READ_MAP | BDI_CAP_WRITE_MAP | BDI_CAP_EXEC_MAP)
+
+#if defined(VM_MAYREAD) && \
+	(BDI_CAP_READ_MAP != VM_MAYREAD || \
+	 BDI_CAP_WRITE_MAP != VM_MAYWRITE || \
+	 BDI_CAP_EXEC_MAP != VM_MAYEXEC)
+#error please change backing_dev_info::capabilities flags
+#endif
+
+extern struct backing_dev_info default_backing_dev_info;
+void default_unplug_io_fn(struct backing_dev_info *bdi, struct page *page);
+
+int writeback_acquire(struct backing_dev_info *bdi);
+int writeback_in_progress(struct backing_dev_info *bdi);
+void writeback_release(struct backing_dev_info *bdi);
+
+static inline int bdi_congested(struct backing_dev_info *bdi, int bdi_bits)
+{
+	if (bdi->congested_fn)
+		return bdi->congested_fn(bdi->congested_data, bdi_bits);
+	return (bdi->state & bdi_bits);
+}
+
+static inline int bdi_read_congested(struct backing_dev_info *bdi)
+{
+	return bdi_congested(bdi, 1 << BDI_read_congested);
+}
+
+static inline int bdi_write_congested(struct backing_dev_info *bdi)
+{
+	return bdi_congested(bdi, 1 << BDI_write_congested);
+}
+
+static inline int bdi_rw_congested(struct backing_dev_info *bdi)
+{
+	return bdi_congested(bdi, (1 << BDI_read_congested)|
+				  (1 << BDI_write_congested));
+}
+
+#define bdi_cap_writeback_dirty(bdi) \
+	(!((bdi)->capabilities & BDI_CAP_NO_WRITEBACK))
+
+#define bdi_cap_account_dirty(bdi) \
+	(!((bdi)->capabilities & BDI_CAP_NO_ACCT_DIRTY))
+
+#define mapping_cap_writeback_dirty(mapping) \
+	bdi_cap_writeback_dirty((mapping)->backing_dev_info)
+
+#define mapping_cap_account_dirty(mapping) \
+	bdi_cap_account_dirty((mapping)->backing_dev_info)
+
+
+#endif		/* _LINUX_BACKING_DEV_H */