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