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From: Nigel Cunningham on 2 Jun 2010 08:30
Add functions that can be used for coalescing and splitting buffers
that are smaller than PAGE_SIZE. These functions provide no method
of determining where the boundaries of the smaller buffers are to
be found - that is the caller's problem.

Signed-off-by: Nigel Cunningham <nigel(a)tuxonice.net>
---
kernel/power/block_io.c | 90 +++++++++++++++++++++++++++++++++++++++++++++++
kernel/power/block_io.h | 4 ++
2 files changed, 94 insertions(+), 0 deletions(-)

diff --git a/kernel/power/block_io.c b/kernel/power/block_io.c
index c449db2..0e57776 100644
--- a/kernel/power/block_io.c
+++ b/kernel/power/block_io.c
@@ -17,6 +17,11 @@

static struct bio *bio_chain;

+static char *hib_ppio_buffer;
+static int hib_ppio_buffer_posn;
+int hib_prepare_buffer(void);
+void hib_free_buffer(void);
+
/**
* submit - submit BIO request.
* @rw: READ or WRITE.
@@ -301,3 +306,88 @@ int swap_read_page(void *buf, int sync)
}
return error;
}
+
+/* Part Page I/O functions */
+static char *hib_ppio_buffer;
+static int hib_ppio_buffer_posn;
+
+int hib_prepare_buffer(void)
+{
+ hib_ppio_buffer = (char *)__get_free_page(__GFP_WAIT);
+ hib_ppio_buffer_posn = 0;
+ return hib_ppio_buffer ? 0 : -ENOMEM;
+}
+
+void hib_free_buffer(void)
+{
+ if (!hib_ppio_buffer)
+ return;
+
+ free_page((unsigned long) hib_ppio_buffer);
+ hib_ppio_buffer = NULL;
+}
+
+int hib_flush_write_buffer(void)
+{
+ return hib_ppio_buffer_posn ? swap_write_page(hib_ppio_buffer, 0) : 0;
+}
+
+int hib_write_buffer(char *buffer, int buffer_size)
+{
+ int bytes_left = buffer_size, result = 0;
+
+ while (bytes_left) {
+ char *from = buffer + buffer_size - bytes_left;
+ char *to = hib_ppio_buffer + hib_ppio_buffer_posn;
+ int capacity = PAGE_SIZE - hib_ppio_buffer_posn;
+
+ if (bytes_left <= capacity) {
+ memcpy(to, from, bytes_left);
+ hib_ppio_buffer_posn += bytes_left;
+ return 0;
+ }
+
+ /* Complete this page and start a new one */
+ memcpy(to, from, capacity);
+ bytes_left -= capacity;
+
+ result = swap_write_page(hib_ppio_buffer, 0);
+ if (result)
+ return result;
+
+ hib_ppio_buffer_posn = 0;
+ }
+
+ return 0;
+}
+
+int hib_read_buffer(char *buffer, int buffer_size)
+{
+ int bytes_left = buffer_size, result = 0;
+
+ while (bytes_left) {
+ char *to = buffer + buffer_size - bytes_left;
+ char *from = hib_ppio_buffer + hib_ppio_buffer_posn;
+ int capacity = PAGE_SIZE - hib_ppio_buffer_posn;
+
+ if (bytes_left <= capacity) {
+ memcpy(to, from, bytes_left);
+ hib_ppio_buffer_posn += bytes_left;
+ return 0;
+ }
+
+ /* Complete this page and start a new one */
+ memcpy(to, from, capacity);
+ bytes_left -= capacity;
+
+ result = swap_read_page(hib_ppio_buffer, 1);
+ if (result) {
+ printk("swap_read_page returned %d.\n", result);
+ return result;
+ }
+
+ hib_ppio_buffer_posn = 0;
+ }
+
+ return 0;
+}
diff --git a/kernel/power/block_io.h b/kernel/power/block_io.h
index 2f91d6d..ac378c5 100644
--- a/kernel/power/block_io.h
+++ b/kernel/power/block_io.h
@@ -21,3 +21,7 @@ int swap_write_page(void *buf, int sync);
int get_swap_reader(unsigned int *flags_p, sector_t first_page);
void release_swap_reader(void);
int swap_read_page(void *buf, int sync);
+int hib_flush_write_buffer(void);
+
+int hib_write_buffer(char *buffer, int len);
+int hib_read_buffer(char *buffer, int len);
--
1.7.0.4

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Next: [PATCH 14/21] Hibernation: Use block extents for reading image