FreeBSD/Linux Kernel Cross Reference
sys/mm/truncate.c

     /*
      * mm/truncate.c - code for taking down pages from address_spaces
      *
      * Copyright (C) 2002, Linus Torvalds
      *
      * 10Sep2002    Andrew Morton
      *              Initial version.
      */
     
    #include <linux/kernel.h>
    #include <linux/backing-dev.h>
    #include <linux/gfp.h>
    #include <linux/mm.h>
    #include <linux/swap.h>
    #include <linux/export.h>
    #include <linux/pagemap.h>
    #include <linux/highmem.h>
    #include <linux/pagevec.h>
    #include <linux/task_io_accounting_ops.h>
    #include <linux/buffer_head.h>  /* grr. try_to_release_page,
                                       do_invalidatepage */
    #include <linux/cleancache.h>
    #include "internal.h"
    
    
    /**
     * do_invalidatepage - invalidate part or all of a page
     * @page: the page which is affected
     * @offset: the index of the truncation point
     *
     * do_invalidatepage() is called when all or part of the page has become
     * invalidated by a truncate operation.
     *
     * do_invalidatepage() does not have to release all buffers, but it must
     * ensure that no dirty buffer is left outside @offset and that no I/O
     * is underway against any of the blocks which are outside the truncation
     * point.  Because the caller is about to free (and possibly reuse) those
     * blocks on-disk.
     */
    void do_invalidatepage(struct page *page, unsigned long offset)
    {
            void (*invalidatepage)(struct page *, unsigned long);
            invalidatepage = page->mapping->a_ops->invalidatepage;
    #ifdef CONFIG_BLOCK
            if (!invalidatepage)
                    invalidatepage = block_invalidatepage;
    #endif
            if (invalidatepage)
                    (*invalidatepage)(page, offset);
    }
    
    static inline void truncate_partial_page(struct page *page, unsigned partial)
    {
            zero_user_segment(page, partial, PAGE_CACHE_SIZE);
            cleancache_invalidate_page(page->mapping, page);
            if (page_has_private(page))
                    do_invalidatepage(page, partial);
    }
    
    /*
     * This cancels just the dirty bit on the kernel page itself, it
     * does NOT actually remove dirty bits on any mmap's that may be
     * around. It also leaves the page tagged dirty, so any sync
     * activity will still find it on the dirty lists, and in particular,
     * clear_page_dirty_for_io() will still look at the dirty bits in
     * the VM.
     *
     * Doing this should *normally* only ever be done when a page
     * is truncated, and is not actually mapped anywhere at all. However,
     * fs/buffer.c does this when it notices that somebody has cleaned
     * out all the buffers on a page without actually doing it through
     * the VM. Can you say "ext3 is horribly ugly"? Tought you could.
     */
    void cancel_dirty_page(struct page *page, unsigned int account_size)
    {
            if (TestClearPageDirty(page)) {
                    struct address_space *mapping = page->mapping;
                    if (mapping && mapping_cap_account_dirty(mapping)) {
                            dec_zone_page_state(page, NR_FILE_DIRTY);
                            dec_bdi_stat(mapping->backing_dev_info,
                                            BDI_RECLAIMABLE);
                            if (account_size)
                                    task_io_account_cancelled_write(account_size);
                    }
            }
    }
    EXPORT_SYMBOL(cancel_dirty_page);
    
    /*
     * If truncate cannot remove the fs-private metadata from the page, the page
     * becomes orphaned.  It will be left on the LRU and may even be mapped into
     * user pagetables if we're racing with filemap_fault().
     *
     * We need to bale out if page->mapping is no longer equal to the original
     * mapping.  This happens a) when the VM reclaimed the page while we waited on
     * its lock, b) when a concurrent invalidate_mapping_pages got there first and
     * c) when tmpfs swizzles a page between a tmpfs inode and swapper_space.
     */
    static int
   truncate_complete_page(struct address_space *mapping, struct page *page)
   {
           if (page->mapping != mapping)
                   return -EIO;
   
           if (page_has_private(page))
                   do_invalidatepage(page, 0);
   
           cancel_dirty_page(page, PAGE_CACHE_SIZE);
   
           ClearPageMappedToDisk(page);
           delete_from_page_cache(page);
           return 0;
   }
   
   /*
    * This is for invalidate_mapping_pages().  That function can be called at
    * any time, and is not supposed to throw away dirty pages.  But pages can
    * be marked dirty at any time too, so use remove_mapping which safely
    * discards clean, unused pages.
    *
    * Returns non-zero if the page was successfully invalidated.
    */
   static int
   invalidate_complete_page(struct address_space *mapping, struct page *page)
   {
           int ret;
   
           if (page->mapping != mapping)
                   return 0;
   
           if (page_has_private(page) && !try_to_release_page(page, 0))
                   return 0;
   
           ret = remove_mapping(mapping, page);
   
           return ret;
   }
   
   int truncate_inode_page(struct address_space *mapping, struct page *page)
   {
           if (page_mapped(page)) {
                   unmap_mapping_range(mapping,
                                      (loff_t)page->index << PAGE_CACHE_SHIFT,
                                      PAGE_CACHE_SIZE, 0);
           }
           return truncate_complete_page(mapping, page);
   }
   
   /*
    * Used to get rid of pages on hardware memory corruption.
    */
   int generic_error_remove_page(struct address_space *mapping, struct page *page)
   {
           if (!mapping)
                   return -EINVAL;
           /*
            * Only punch for normal data pages for now.
            * Handling other types like directories would need more auditing.
            */
           if (!S_ISREG(mapping->host->i_mode))
                   return -EIO;
           return truncate_inode_page(mapping, page);
   }
   EXPORT_SYMBOL(generic_error_remove_page);
   
   /*
    * Safely invalidate one page from its pagecache mapping.
    * It only drops clean, unused pages. The page must be locked.
    *
    * Returns 1 if the page is successfully invalidated, otherwise 0.
    */
   int invalidate_inode_page(struct page *page)
   {
           struct address_space *mapping = page_mapping(page);
           if (!mapping)
                   return 0;
           if (PageDirty(page) || PageWriteback(page))
                   return 0;
           if (page_mapped(page))
                   return 0;
           return invalidate_complete_page(mapping, page);
   }
   
   /**
    * truncate_inode_pages_range - truncate range of pages specified by start & end byte offsets
    * @mapping: mapping to truncate
    * @lstart: offset from which to truncate
    * @lend: offset to which to truncate
    *
    * Truncate the page cache, removing the pages that are between
    * specified offsets (and zeroing out partial page
    * (if lstart is not page aligned)).
    *
    * Truncate takes two passes - the first pass is nonblocking.  It will not
    * block on page locks and it will not block on writeback.  The second pass
    * will wait.  This is to prevent as much IO as possible in the affected region.
    * The first pass will remove most pages, so the search cost of the second pass
    * is low.
    *
    * We pass down the cache-hot hint to the page freeing code.  Even if the
    * mapping is large, it is probably the case that the final pages are the most
    * recently touched, and freeing happens in ascending file offset order.
    */
   void truncate_inode_pages_range(struct address_space *mapping,
                                   loff_t lstart, loff_t lend)
   {
           const pgoff_t start = (lstart + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT;
           const unsigned partial = lstart & (PAGE_CACHE_SIZE - 1);
           struct pagevec pvec;
           pgoff_t index;
           pgoff_t end;
           int i;
   
           cleancache_invalidate_inode(mapping);
           if (mapping->nrpages == 0)
                   return;
   
           BUG_ON((lend & (PAGE_CACHE_SIZE - 1)) != (PAGE_CACHE_SIZE - 1));
           end = (lend >> PAGE_CACHE_SHIFT);
   
           pagevec_init(&pvec, 0);
           index = start;
           while (index <= end && pagevec_lookup(&pvec, mapping, index,
                           min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1)) {
                   mem_cgroup_uncharge_start();
                   for (i = 0; i < pagevec_count(&pvec); i++) {
                           struct page *page = pvec.pages[i];
   
                           /* We rely upon deletion not changing page->index */
                           index = page->index;
                           if (index > end)
                                   break;
   
                           if (!trylock_page(page))
                                   continue;
                           WARN_ON(page->index != index);
                           if (PageWriteback(page)) {
                                   unlock_page(page);
                                   continue;
                           }
                           truncate_inode_page(mapping, page);
                           unlock_page(page);
                   }
                   pagevec_release(&pvec);
                   mem_cgroup_uncharge_end();
                   cond_resched();
                   index++;
           }
   
           if (partial) {
                   struct page *page = find_lock_page(mapping, start - 1);
                   if (page) {
                           wait_on_page_writeback(page);
                           truncate_partial_page(page, partial);
                           unlock_page(page);
                           page_cache_release(page);
                   }
           }
   
           index = start;
           for ( ; ; ) {
                   cond_resched();
                   if (!pagevec_lookup(&pvec, mapping, index,
                           min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1)) {
                           if (index == start)
                                   break;
                           index = start;
                           continue;
                   }
                   if (index == start && pvec.pages[0]->index > end) {
                           pagevec_release(&pvec);
                           break;
                   }
                   mem_cgroup_uncharge_start();
                   for (i = 0; i < pagevec_count(&pvec); i++) {
                           struct page *page = pvec.pages[i];
   
                           /* We rely upon deletion not changing page->index */
                           index = page->index;
                           if (index > end)
                                   break;
   
                           lock_page(page);
                           WARN_ON(page->index != index);
                           wait_on_page_writeback(page);
                           truncate_inode_page(mapping, page);
                           unlock_page(page);
                   }
                   pagevec_release(&pvec);
                   mem_cgroup_uncharge_end();
                   index++;
           }
           cleancache_invalidate_inode(mapping);
   }
   EXPORT_SYMBOL(truncate_inode_pages_range);
   
   /**
    * truncate_inode_pages - truncate *all* the pages from an offset
    * @mapping: mapping to truncate
    * @lstart: offset from which to truncate
    *
    * Called under (and serialised by) inode->i_mutex.
    *
    * Note: When this function returns, there can be a page in the process of
    * deletion (inside __delete_from_page_cache()) in the specified range.  Thus
    * mapping->nrpages can be non-zero when this function returns even after
    * truncation of the whole mapping.
    */
   void truncate_inode_pages(struct address_space *mapping, loff_t lstart)
   {
           truncate_inode_pages_range(mapping, lstart, (loff_t)-1);
   }
   EXPORT_SYMBOL(truncate_inode_pages);
   
   /**
    * invalidate_mapping_pages - Invalidate all the unlocked pages of one inode
    * @mapping: the address_space which holds the pages to invalidate
    * @start: the offset 'from' which to invalidate
    * @end: the offset 'to' which to invalidate (inclusive)
    *
    * This function only removes the unlocked pages, if you want to
    * remove all the pages of one inode, you must call truncate_inode_pages.
    *
    * invalidate_mapping_pages() will not block on IO activity. It will not
    * invalidate pages which are dirty, locked, under writeback or mapped into
    * pagetables.
    */
   unsigned long invalidate_mapping_pages(struct address_space *mapping,
                   pgoff_t start, pgoff_t end)
   {
           struct pagevec pvec;
           pgoff_t index = start;
           unsigned long ret;
           unsigned long count = 0;
           int i;
   
           /*
            * Note: this function may get called on a shmem/tmpfs mapping:
            * pagevec_lookup() might then return 0 prematurely (because it
            * got a gangful of swap entries); but it's hardly worth worrying
            * about - it can rarely have anything to free from such a mapping
            * (most pages are dirty), and already skips over any difficulties.
            */
   
           pagevec_init(&pvec, 0);
           while (index <= end && pagevec_lookup(&pvec, mapping, index,
                           min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1)) {
                   mem_cgroup_uncharge_start();
                   for (i = 0; i < pagevec_count(&pvec); i++) {
                           struct page *page = pvec.pages[i];
   
                           /* We rely upon deletion not changing page->index */
                           index = page->index;
                           if (index > end)
                                   break;
   
                           if (!trylock_page(page))
                                   continue;
                           WARN_ON(page->index != index);
                           ret = invalidate_inode_page(page);
                           unlock_page(page);
                           /*
                            * Invalidation is a hint that the page is no longer
                            * of interest and try to speed up its reclaim.
                            */
                           if (!ret)
                                   deactivate_page(page);
                           count += ret;
                   }
                   pagevec_release(&pvec);
                   mem_cgroup_uncharge_end();
                   cond_resched();
                   index++;
           }
           return count;
   }
   EXPORT_SYMBOL(invalidate_mapping_pages);
   
   /*
    * This is like invalidate_complete_page(), except it ignores the page's
    * refcount.  We do this because invalidate_inode_pages2() needs stronger
    * invalidation guarantees, and cannot afford to leave pages behind because
    * shrink_page_list() has a temp ref on them, or because they're transiently
    * sitting in the lru_cache_add() pagevecs.
    */
   static int
   invalidate_complete_page2(struct address_space *mapping, struct page *page)
   {
           if (page->mapping != mapping)
                   return 0;
   
           if (page_has_private(page) && !try_to_release_page(page, GFP_KERNEL))
                   return 0;
   
           spin_lock_irq(&mapping->tree_lock);
           if (PageDirty(page))
                   goto failed;
   
           BUG_ON(page_has_private(page));
           __delete_from_page_cache(page);
           spin_unlock_irq(&mapping->tree_lock);
           mem_cgroup_uncharge_cache_page(page);
   
           if (mapping->a_ops->freepage)
                   mapping->a_ops->freepage(page);
   
           page_cache_release(page);       /* pagecache ref */
           return 1;
   failed:
           spin_unlock_irq(&mapping->tree_lock);
           return 0;
   }
   
   static int do_launder_page(struct address_space *mapping, struct page *page)
   {
           if (!PageDirty(page))
                   return 0;
           if (page->mapping != mapping || mapping->a_ops->launder_page == NULL)
                   return 0;
           return mapping->a_ops->launder_page(page);
   }
   
   /**
    * invalidate_inode_pages2_range - remove range of pages from an address_space
    * @mapping: the address_space
    * @start: the page offset 'from' which to invalidate
    * @end: the page offset 'to' which to invalidate (inclusive)
    *
    * Any pages which are found to be mapped into pagetables are unmapped prior to
    * invalidation.
    *
    * Returns -EBUSY if any pages could not be invalidated.
    */
   int invalidate_inode_pages2_range(struct address_space *mapping,
                                     pgoff_t start, pgoff_t end)
   {
           struct pagevec pvec;
           pgoff_t index;
           int i;
           int ret = 0;
           int ret2 = 0;
           int did_range_unmap = 0;
   
           cleancache_invalidate_inode(mapping);
           pagevec_init(&pvec, 0);
           index = start;
           while (index <= end && pagevec_lookup(&pvec, mapping, index,
                           min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1)) {
                   mem_cgroup_uncharge_start();
                   for (i = 0; i < pagevec_count(&pvec); i++) {
                           struct page *page = pvec.pages[i];
   
                           /* We rely upon deletion not changing page->index */
                           index = page->index;
                           if (index > end)
                                   break;
   
                           lock_page(page);
                           WARN_ON(page->index != index);
                           if (page->mapping != mapping) {
                                   unlock_page(page);
                                   continue;
                           }
                           wait_on_page_writeback(page);
                           if (page_mapped(page)) {
                                   if (!did_range_unmap) {
                                           /*
                                            * Zap the rest of the file in one hit.
                                            */
                                           unmap_mapping_range(mapping,
                                              (loff_t)index << PAGE_CACHE_SHIFT,
                                              (loff_t)(1 + end - index)
                                                            << PAGE_CACHE_SHIFT,
                                               0);
                                           did_range_unmap = 1;
                                   } else {
                                           /*
                                            * Just zap this page
                                            */
                                           unmap_mapping_range(mapping,
                                              (loff_t)index << PAGE_CACHE_SHIFT,
                                              PAGE_CACHE_SIZE, 0);
                                   }
                           }
                           BUG_ON(page_mapped(page));
                           ret2 = do_launder_page(mapping, page);
                           if (ret2 == 0) {
                                   if (!invalidate_complete_page2(mapping, page))
                                           ret2 = -EBUSY;
                           }
                           if (ret2 < 0)
                                   ret = ret2;
                           unlock_page(page);
                   }
                   pagevec_release(&pvec);
                   mem_cgroup_uncharge_end();
                   cond_resched();
                   index++;
           }
           cleancache_invalidate_inode(mapping);
           return ret;
   }
   EXPORT_SYMBOL_GPL(invalidate_inode_pages2_range);
   
   /**
    * invalidate_inode_pages2 - remove all pages from an address_space
    * @mapping: the address_space
    *
    * Any pages which are found to be mapped into pagetables are unmapped prior to
    * invalidation.
    *
    * Returns -EBUSY if any pages could not be invalidated.
    */
   int invalidate_inode_pages2(struct address_space *mapping)
   {
           return invalidate_inode_pages2_range(mapping, 0, -1);
   }
   EXPORT_SYMBOL_GPL(invalidate_inode_pages2);
   
   /**
    * truncate_pagecache - unmap and remove pagecache that has been truncated
    * @inode: inode
    * @oldsize: old file size
    * @newsize: new file size
    *
    * inode's new i_size must already be written before truncate_pagecache
    * is called.
    *
    * This function should typically be called before the filesystem
    * releases resources associated with the freed range (eg. deallocates
    * blocks). This way, pagecache will always stay logically coherent
    * with on-disk format, and the filesystem would not have to deal with
    * situations such as writepage being called for a page that has already
    * had its underlying blocks deallocated.
    */
   void truncate_pagecache(struct inode *inode, loff_t oldsize, loff_t newsize)
   {
           struct address_space *mapping = inode->i_mapping;
           loff_t holebegin = round_up(newsize, PAGE_SIZE);
   
           /*
            * unmap_mapping_range is called twice, first simply for
            * efficiency so that truncate_inode_pages does fewer
            * single-page unmaps.  However after this first call, and
            * before truncate_inode_pages finishes, it is possible for
            * private pages to be COWed, which remain after
            * truncate_inode_pages finishes, hence the second
            * unmap_mapping_range call must be made for correctness.
            */
           unmap_mapping_range(mapping, holebegin, 0, 1);
           truncate_inode_pages(mapping, newsize);
           unmap_mapping_range(mapping, holebegin, 0, 1);
   }
   EXPORT_SYMBOL(truncate_pagecache);
   
   /**
    * truncate_setsize - update inode and pagecache for a new file size
    * @inode: inode
    * @newsize: new file size
    *
    * truncate_setsize updates i_size and performs pagecache truncation (if
    * necessary) to @newsize. It will be typically be called from the filesystem's
    * setattr function when ATTR_SIZE is passed in.
    *
    * Must be called with inode_mutex held and before all filesystem specific
    * block truncation has been performed.
    */
   void truncate_setsize(struct inode *inode, loff_t newsize)
   {
           loff_t oldsize;
   
           oldsize = inode->i_size;
           i_size_write(inode, newsize);
   
           truncate_pagecache(inode, oldsize, newsize);
   }
   EXPORT_SYMBOL(truncate_setsize);
   
   /**
    * truncate_pagecache_range - unmap and remove pagecache that is hole-punched
    * @inode: inode
    * @lstart: offset of beginning of hole
    * @lend: offset of last byte of hole
    *
    * This function should typically be called before the filesystem
    * releases resources associated with the freed range (eg. deallocates
    * blocks). This way, pagecache will always stay logically coherent
    * with on-disk format, and the filesystem would not have to deal with
    * situations such as writepage being called for a page that has already
    * had its underlying blocks deallocated.
    */
   void truncate_pagecache_range(struct inode *inode, loff_t lstart, loff_t lend)
   {
           struct address_space *mapping = inode->i_mapping;
           loff_t unmap_start = round_up(lstart, PAGE_SIZE);
           loff_t unmap_end = round_down(1 + lend, PAGE_SIZE) - 1;
           /*
            * This rounding is currently just for example: unmap_mapping_range
            * expands its hole outwards, whereas we want it to contract the hole
            * inwards.  However, existing callers of truncate_pagecache_range are
            * doing their own page rounding first; and truncate_inode_pages_range
            * currently BUGs if lend is not pagealigned-1 (it handles partial
            * page at start of hole, but not partial page at end of hole).  Note
            * unmap_mapping_range allows holelen 0 for all, and we allow lend -1.
            */
   
           /*
            * Unlike in truncate_pagecache, unmap_mapping_range is called only
            * once (before truncating pagecache), and without "even_cows" flag:
            * hole-punching should not remove private COWed pages from the hole.
            */
           if ((u64)unmap_end > (u64)unmap_start)
                   unmap_mapping_range(mapping, unmap_start,
                                       1 + unmap_end - unmap_start, 0);
           truncate_inode_pages_range(mapping, lstart, lend);
   }
   EXPORT_SYMBOL(truncate_pagecache_range);

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