Department of Computer Science
University of São Paulo
São Paulo, Brazil

description

functions

---

• static int swap_writepage(struct page *page)

  description

  This function just calls rw_swap_page() , with a WRITE parameter and 0 wait. That will do an asynchronous write of this page on to the swap device. This function is currently only called from page_launder() .

  parameters

  • page - The page in swap cache to swap out.

  return value

  • return 0 always.

  ---

• void show_swap_cache_info (void)

  description

  All this function does is printk some swap cache information. It's called from show_free_areas_core() , but only if the SWAP_CACHE_INFO symbol is defined.

  parameters

  • none

  return value

  • none

  ---

• void add_to_swap_cache(struct page *page, swp_entry_t entry)

  description

  This function is called when we want to add a page to swap cache. Basically what it does is set some flags (page->flags), in special with the PG_swap_cache attribute, and most importantly, add it to the page cache (using add_to_page_cache_locked() ).
  It is called from two places in VM:
  • It is mainly called from try_to_swap_out() , when we're trying to swap out a page and we've found and dirty, swappable page.
  • It is also called from read_swap_cache_async() , when we're looking for a page in swap cache, but it's not there anymore, so we get it from swap and add it to the swap cache.

  parameters

  • page - the address of page to add in swap cache
  • entry - the swap entry that contains the index for this page

  return value

  • none

  ---

• static inline void remove_from_swap_cache (struct page *page)

  description

  This function is called when we are removing a page from swap_cache. This is an internal function and is called only by __delete_from_swap_cache() . It basically:
  • Clears the PG_swap_cache modifier from the page's flags.
  • Clears the PG_dirty modifier from the page's flags.
  • Removes that page from the page_cache by calling __remove_inode_page() .

  parameters

  • page - the page to remove from swap cache.

  return value

  • none

  ---

• void __delete_from_swap_cache(struct page *page)

  description

  This function is called to delete a page from swap_cache and is used as a wrapper to remove_from_swap_cache for external use, but must only be called on pages that have been verified to be in swap_cache.
  • Calls remove_from_swap_cache .
  • Also removes this entry (page->index) from swap_list, calling swap_free()

  parameters

  • page - page to be deleted from swap_cache.

  return value

  • none

  ---

• void delete_from_swap_cache_nolock(struct page *page)

  description

  This function does two things, primarily:
  • Locks pagecache_lock
  • Calls __delete_from_swap_cache to remove it's PG_swap_cache, and remove it from the page_cache.
  • Clears PG_Dirty bit from the page's flags.
  • Unlocks pagecache_lock

  parameters

  • page - page to be deleted from swap_cache.

  return value

  • none

  ---

• void delete_from_swap_cache(struct page *page)

  description

  This is just a wrapper to delete_from_swap_cache_nolock() with calls to lock_page() and UnlockPage() surrounding it. This is a called from:
  • try_to_unuse() when turning off the swap system.
  • shmem_free_swp () when shmem does it's delete_inode operations.

  parameters

  • page - page to be deleted from swap_cache.

  return value

  • none

  ---

• void free_page_and_swap_cache(struct page *page)

  description

  • It basicaly performs a free_page(), also freeing any swap cache associated with this page if it is the last user of the page.

  parameters

  • page - page to be deleted from swap_cache.

  return value

  • none

  ---

• struct page * lookup_swap_cache(swp_entry_t entry)

  description

  Lookup a swap entry in the swap cache.
  • Call find_lock_page function to look for the page
  • If not found, return 0
  • Check then if it was removed by refill_inactive_scan, etc. If it was, it is released and re-search.
  • Otherwise, check if it is really a swapper swap page
  • Unlock and return it

  parameters

  • entry - entry to be searched

  return value

  • 0 - not found
  • found - pointer to the page found

  ---

• struct page * read_swap_cache_async(swp_entry_t entry, int wait)

  description

  Locate a page of swap in physical memory, reserving swap cache space and reading the disk if it is not already cached. If wait==0, we are only doing readahead, so don't worry if the page is already locked.
  • Make sure the swap entry is still in use, through swap_duplicate().
  • Look for the page in the swap cache calling lookup_swap_cache
  • If found, swap entry is freed (swap_free())
  • If not, a new page is obtained by calling __get_free_page().
  • Check the swap cache again, in case we stalled above.
  • If it was found, besides freeing swap entry, the new page is release (page_cache_release())
  • Add it to the swap cache (add_to_swap_cache())
  • Read its contents (rw_swap_page())

  parameters

  • entry - entry to be searched
  • wait - passed as parameter to rw_swap_page(). If wait == 1, we wait on page. Otherwise, we are only doing readahead.

  return value

  • 0 - new page allocated and read its contents
  • 1 - found the page in swap cache

Page last updated on "Thu Apr 19 09:29:45 2001"
Send feedback to Rodrigo S. de Castro<[email protected]>