Add comments describing struct snapshot_handle and its members,
change the confusing name of its member 'page' to 'cur'.
Signed-off-by: Rafael J. Wysocki <[email protected]>
---
kernel/power/power.h | 64 ++++++++++++++++++++++++++++++++++++++++++------
kernel/power/snapshot.c | 40 +++++++++++++++---------------
2 files changed, 76 insertions(+), 28 deletions(-)
Index: linux-2.6.18-rc1-mm1/kernel/power/power.h
===================================================================
--- linux-2.6.18-rc1-mm1.orig/kernel/power/power.h
+++ linux-2.6.18-rc1-mm1/kernel/power/power.h
@@ -50,17 +50,65 @@ extern asmlinkage int swsusp_arch_resume
extern unsigned int count_data_pages(void);
+/**
+ * Auxiliary structure used for reading the snapshot image data and
+ * metadata from and writing them to the list of page backup entries
+ * (PBEs) which is the main data structure of swsusp.
+ *
+ * Using struct snapshot_handle we can transfer the image, including its
+ * metadata, as a continuous sequence of bytes with the help of
+ * snapshot_read_next() and snapshot_write_next().
+ *
+ * The code that writes the image to a storage or transfers it to
+ * the user land is required to use snapshot_read_next() for this
+ * purpose and it should not make any assumptions regarding the internal
+ * structure of the image. Similarly, the code that reads the image from
+ * a storage or transfers it from the user land is required to use
+ * snapshot_write_next().
+ *
+ * This may allow us to change the internal structure of the image
+ * in the future with considerably less effort.
+ */
+
struct snapshot_handle {
- loff_t offset;
- unsigned int page;
- unsigned int page_offset;
- unsigned int prev;
- struct pbe *pbe, *last_pbe;
- void *buffer;
- unsigned int buf_offset;
- int sync_read;
+ loff_t offset; /* number of the last byte ready for reading
+ * or writing in the sequence
+ */
+ unsigned int cur; /* number of the block of PAGE_SIZE bytes the
+ * next operation will refer to (ie. current)
+ */
+ unsigned int cur_offset; /* offset with respect to the current
+ * block (for the next operation)
+ */
+ unsigned int prev; /* number of the block of PAGE_SIZE bytes that
+ * was the current one previously
+ */
+ struct pbe *pbe; /* PBE that corresponds to 'buffer' */
+ struct pbe *last_pbe; /* When the image is restored (eg. read
+ * from disk) we can store some image
+ * data directly in the page frames
+ * in which they were before suspend.
+ * In such a case the PBEs that
+ * correspond to them will be unused.
+ * This is the last PBE, so far, that
+ * does not correspond to such data.
+ */
+ void *buffer; /* address of the block to read from
+ * or write to
+ */
+ unsigned int buf_offset; /* location to read from or write to,
+ * given as a displacement from 'buffer'
+ */
+ int sync_read; /* Set to one to notify the caller of
+ * snapshot_write_next() that it may
+ * need to call wait_on_bio_chain()
+ */
};
+/* This macro returns the address from/to which the caller of
+ * snapshot_read_next()/snapshot_write_next() is allowed to
+ * read/write data after the function returns
+ */
#define data_of(handle) ((handle).buffer + (handle).buf_offset)
extern int snapshot_read_next(struct snapshot_handle *handle, size_t count);
Index: linux-2.6.18-rc1-mm1/kernel/power/snapshot.c
===================================================================
--- linux-2.6.18-rc1-mm1.orig/kernel/power/snapshot.c
+++ linux-2.6.18-rc1-mm1/kernel/power/snapshot.c
@@ -555,7 +555,7 @@ static inline struct pbe *pack_orig_addr
int snapshot_read_next(struct snapshot_handle *handle, size_t count)
{
- if (handle->page > nr_meta_pages + nr_copy_pages)
+ if (handle->cur > nr_meta_pages + nr_copy_pages)
return 0;
if (!buffer) {
/* This makes the buffer be freed by swsusp_free() */
@@ -568,8 +568,8 @@ int snapshot_read_next(struct snapshot_h
handle->buffer = buffer;
handle->pbe = pagedir_nosave;
}
- if (handle->prev < handle->page) {
- if (handle->page <= nr_meta_pages) {
+ if (handle->prev < handle->cur) {
+ if (handle->cur <= nr_meta_pages) {
handle->pbe = pack_orig_addresses(buffer, handle->pbe);
if (!handle->pbe)
handle->pbe = pagedir_nosave;
@@ -577,15 +577,15 @@ int snapshot_read_next(struct snapshot_h
handle->buffer = (void *)handle->pbe->address;
handle->pbe = handle->pbe->next;
}
- handle->prev = handle->page;
+ handle->prev = handle->cur;
}
- handle->buf_offset = handle->page_offset;
- if (handle->page_offset + count >= PAGE_SIZE) {
- count = PAGE_SIZE - handle->page_offset;
- handle->page_offset = 0;
- handle->page++;
+ handle->buf_offset = handle->cur_offset;
+ if (handle->cur_offset + count >= PAGE_SIZE) {
+ count = PAGE_SIZE - handle->cur_offset;
+ handle->cur_offset = 0;
+ handle->cur++;
} else {
- handle->page_offset += count;
+ handle->cur_offset += count;
}
handle->offset += count;
return count;
@@ -820,7 +820,7 @@ int snapshot_write_next(struct snapshot_
{
int error = 0;
- if (handle->prev && handle->page > nr_meta_pages + nr_copy_pages)
+ if (handle->prev && handle->cur > nr_meta_pages + nr_copy_pages)
return 0;
if (!buffer) {
/* This makes the buffer be freed by swsusp_free() */
@@ -831,7 +831,7 @@ int snapshot_write_next(struct snapshot_
if (!handle->offset)
handle->buffer = buffer;
handle->sync_read = 1;
- if (handle->prev < handle->page) {
+ if (handle->prev < handle->cur) {
if (!handle->prev) {
error = load_header(handle,
(struct swsusp_info *)buffer);
@@ -854,15 +854,15 @@ int snapshot_write_next(struct snapshot_
handle->buffer = get_buffer(handle);
handle->sync_read = 0;
}
- handle->prev = handle->page;
+ handle->prev = handle->cur;
}
- handle->buf_offset = handle->page_offset;
- if (handle->page_offset + count >= PAGE_SIZE) {
- count = PAGE_SIZE - handle->page_offset;
- handle->page_offset = 0;
- handle->page++;
+ handle->buf_offset = handle->cur_offset;
+ if (handle->cur_offset + count >= PAGE_SIZE) {
+ count = PAGE_SIZE - handle->cur_offset;
+ handle->cur_offset = 0;
+ handle->cur++;
} else {
- handle->page_offset += count;
+ handle->cur_offset += count;
}
handle->offset += count;
return count;
@@ -871,5 +871,5 @@ int snapshot_write_next(struct snapshot_
int snapshot_image_loaded(struct snapshot_handle *handle)
{
return !(!handle->pbe || handle->pbe->next || !nr_copy_pages ||
- handle->page <= nr_meta_pages + nr_copy_pages);
+ handle->cur <= nr_meta_pages + nr_copy_pages);
}
-
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