Commit fb13a28b authored by Rafael J. Wysocki's avatar Rafael J. Wysocki Committed by Linus Torvalds

[PATCH] swsusp: struct snapshot_handle cleanup

Add comments describing struct snapshot_handle and its members, change the
confusing name of its member 'page' to 'cur'.
Signed-off-by: default avatarRafael J. Wysocki <rjw@sisk.pl>
Cc: Pavel Machek <pavel@ucw.cz>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent ae83c5ee
......@@ -50,17 +50,65 @@ extern asmlinkage int swsusp_arch_resume(void);
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);
......
......@@ -555,7 +555,7 @@ static inline struct pbe *pack_orig_addresses(unsigned long *buf, struct pbe *pb
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_handle *handle, size_t count)
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_handle *handle, size_t count)
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_handle *handle, size_t count)
{
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_handle *handle, size_t count)
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 *handle, size_t count)
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_handle *handle, size_t count)
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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