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	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * 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/dax.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 */
 #include <linux/shmem_fs.h>
 #include <linux/rmap.h>
 #include "internal.h"
 
 /*
  * Regular page slots are stabilized by the page lock even without the tree
  * itself locked.  These unlocked entries need verification under the tree
  * lock.
  */
 static inline void __clear_shadow_entry(struct address_space *mapping,
                 pgoff_t index, void *entry)
 {
     XA_STATE(xas, &mapping->i_pages, index);
 
     xas_set_update(&xas, workingset_update_node);
     if (xas_load(&xas) != entry)
         return;
     xas_store(&xas, NULL);
 }
 
 static void clear_shadow_entry(struct address_space *mapping, pgoff_t index,
                    void *entry)
 {
     spin_lock(&mapping->host->i_lock);
     xa_lock_irq(&mapping->i_pages);
     __clear_shadow_entry(mapping, index, entry);
     xa_unlock_irq(&mapping->i_pages);
     if (mapping_shrinkable(mapping))
         inode_add_lru(mapping->host);
     spin_unlock(&mapping->host->i_lock);
 }
 
 /*
  * Unconditionally remove exceptional entries. Usually called from truncate
  * path. Note that the folio_batch may be altered by this function by removing
  * exceptional entries similar to what folio_batch_remove_exceptionals() does.
  */
 static void truncate_folio_batch_exceptionals(struct address_space *mapping,
                 struct folio_batch *fbatch, pgoff_t *indices)
 {
     int i, j;
     bool dax;
 
     /* Handled by shmem itself */
     if (shmem_mapping(mapping))
         return;
 
     for (j = 0; j < folio_batch_count(fbatch); j++)
         if (xa_is_value(fbatch->folios[j]))
             break;
 
     if (j == folio_batch_count(fbatch))
         return;
 
     dax = dax_mapping(mapping);
     if (!dax) {
         spin_lock(&mapping->host->i_lock);
         xa_lock_irq(&mapping->i_pages);
     }
 
     for (i = j; i < folio_batch_count(fbatch); i++) {
         struct folio *folio = fbatch->folios[i];
         pgoff_t index = indices[i];
 
         if (!xa_is_value(folio)) {
             fbatch->folios[j++] = folio;
             continue;
         }
 
         if (unlikely(dax)) {
             dax_delete_mapping_entry(mapping, index);
             continue;
         }
 
         __clear_shadow_entry(mapping, index, folio);
     }
 
     if (!dax) {
         xa_unlock_irq(&mapping->i_pages);
         if (mapping_shrinkable(mapping))
             inode_add_lru(mapping->host);
         spin_unlock(&mapping->host->i_lock);
     }
     fbatch->nr = j;
 }
 
 /*
  * Invalidate exceptional entry if easily possible. This handles exceptional
  * entries for invalidate_inode_pages().
  */
 static int invalidate_exceptional_entry(struct address_space *mapping,
                     pgoff_t index, void *entry)
 {
     /* Handled by shmem itself, or for DAX we do nothing. */
     if (shmem_mapping(mapping) || dax_mapping(mapping))
         return 1;
     clear_shadow_entry(mapping, index, entry);
     return 1;
 }
 
 /*
  * Invalidate exceptional entry if clean. This handles exceptional entries for
  * invalidate_inode_pages2() so for DAX it evicts only clean entries.
  */
 static int invalidate_exceptional_entry2(struct address_space *mapping,
                      pgoff_t index, void *entry)
 {
     /* Handled by shmem itself */
     if (shmem_mapping(mapping))
         return 1;
     if (dax_mapping(mapping))
         return dax_invalidate_mapping_entry_sync(mapping, index);
     clear_shadow_entry(mapping, index, entry);
     return 1;
 }
 
 /**
  * folio_invalidate - Invalidate part or all of a folio.
  * @folio: The folio which is affected.
  * @offset: start of the range to invalidate
  * @length: length of the range to invalidate
  *
  * folio_invalidate() is called when all or part of the folio has become
  * invalidated by a truncate operation.
  *
  * folio_invalidate() 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 folio_invalidate(struct folio *folio, size_t offset, size_t length)
 {
     const struct address_space_operations *aops = folio->mapping->a_ops;
 
     if (aops->invalidate_folio)
         aops->invalidate_folio(folio, offset, length);
 }
 EXPORT_SYMBOL_GPL(folio_invalidate);
 
 /*
  * 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 bail 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 void truncate_cleanup_folio(struct folio *folio)
 {
     if (folio_mapped(folio))
         unmap_mapping_folio(folio);
 
     if (folio_has_private(folio))
         folio_invalidate(folio, 0, folio_size(folio));
 
     /*
      * Some filesystems seem to re-dirty the page even after
      * the VM has canceled the dirty bit (eg ext3 journaling).
      * Hence dirty accounting check is placed after invalidation.
      */
     folio_cancel_dirty(folio);
     folio_clear_mappedtodisk(folio);
 }
 
 int truncate_inode_folio(struct address_space *mapping, struct folio *folio)
 {
     if (folio->mapping != mapping)
         return -EIO;
 
     truncate_cleanup_folio(folio);
     filemap_remove_folio(folio);
     return 0;
 }
 
 /*
  * Handle partial folios.  The folio may be entirely within the
  * range if a split has raced with us.  If not, we zero the part of the
  * folio that's within the [start, end] range, and then split the folio if
  * it's large.  split_page_range() will discard pages which now lie beyond
  * i_size, and we rely on the caller to discard pages which lie within a
  * newly created hole.
  *
  * Returns false if splitting failed so the caller can avoid
  * discarding the entire folio which is stubbornly unsplit.
  */
 bool truncate_inode_partial_folio(struct folio *folio, loff_t start, loff_t end)
 {
     loff_t pos = folio_pos(folio);
     unsigned int offset, length;
 
     if (pos < start)
         offset = start - pos;
     else
         offset = 0;
     length = folio_size(folio);
     if (pos + length <= (u64)end)
         length = length - offset;
     else
         length = end + 1 - pos - offset;
 
     folio_wait_writeback(folio);
     if (length == folio_size(folio)) {
         truncate_inode_folio(folio->mapping, folio);
         return true;
     }
 
     /*
      * We may be zeroing pages we're about to discard, but it avoids
      * doing a complex calculation here, and then doing the zeroing
      * anyway if the page split fails.
      */
     folio_zero_range(folio, offset, length);
 
     if (folio_has_private(folio))
         folio_invalidate(folio, offset, length);
     if (!folio_test_large(folio))
         return true;
     if (split_huge_page(&folio->page) == 0)
         return true;
     if (folio_test_dirty(folio))
         return false;
     truncate_inode_folio(folio->mapping, folio);
     return true;
 }
 
 /*
  * Used to get rid of pages on hardware memory corruption.
  */
 int generic_error_remove_page(struct address_space *mapping, struct page *page)
 {
     VM_BUG_ON_PAGE(PageTail(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_folio(mapping, page_folio(page));
 }
 EXPORT_SYMBOL(generic_error_remove_page);
 
 static long mapping_evict_folio(struct address_space *mapping,
         struct folio *folio)
 {
     if (folio_test_dirty(folio) || folio_test_writeback(folio))
         return 0;
     /* The refcount will be elevated if any page in the folio is mapped */
     if (folio_ref_count(folio) >
             folio_nr_pages(folio) + folio_has_private(folio) + 1)
         return 0;
     if (folio_has_private(folio) && !filemap_release_folio(folio, 0))
         return 0;
 
     return remove_mapping(mapping, folio);
 }
 
 /**
  * invalidate_inode_page() - Remove an unused page from the pagecache.
  * @page: The page to remove.
  *
  * Safely invalidate one page from its pagecache mapping.
  * It only drops clean, unused pages.
  *
  * Context: Page must be locked.
  * Return: The number of pages successfully removed.
  */
 long invalidate_inode_page(struct page *page)
 {
     struct folio *folio = page_folio(page);
     struct address_space *mapping = folio_mapping(folio);
 
     /* The page may have been truncated before it was locked */
     if (!mapping)
         return 0;
     return mapping_evict_folio(mapping, folio);
 }
 
 /**
  * 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 (inclusive)
  *
  * Truncate the page cache, removing the pages that are between
  * specified offsets (and zeroing out partial pages
  * if lstart or lend + 1 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.
  *
  * Note that since ->invalidate_folio() accepts range to invalidate
  * truncate_inode_pages_range is able to handle cases where lend + 1 is not
  * page aligned properly.
  */
 void truncate_inode_pages_range(struct address_space *mapping,
                 loff_t lstart, loff_t lend)
 {
     pgoff_t     start;      /* inclusive */
     pgoff_t     end;        /* exclusive */
     struct folio_batch fbatch;
     pgoff_t     indices[PAGEVEC_SIZE];
     pgoff_t     index;
     int     i;
     struct folio    *folio;
     bool        same_folio;
 
     if (mapping_empty(mapping))
         return;
 
     /*
      * 'start' and 'end' always covers the range of pages to be fully
      * truncated. Partial pages are covered with 'partial_start' at the
      * start of the range and 'partial_end' at the end of the range.
      * Note that 'end' is exclusive while 'lend' is inclusive.
      */
     start = (lstart + PAGE_SIZE - 1) >> PAGE_SHIFT;
     if (lend == -1)
         /*
          * lend == -1 indicates end-of-file so we have to set 'end'
          * to the highest possible pgoff_t and since the type is
          * unsigned we're using -1.
          */
         end = -1;
     else
         end = (lend + 1) >> PAGE_SHIFT;
 
     folio_batch_init(&fbatch);
     index = start;
     while (index < end && find_lock_entries(mapping, index, end - 1,
             &fbatch, indices)) {
         index = indices[folio_batch_count(&fbatch) - 1] + 1;
         truncate_folio_batch_exceptionals(mapping, &fbatch, indices);
         for (i = 0; i < folio_batch_count(&fbatch); i++)
             truncate_cleanup_folio(fbatch.folios[i]);
         delete_from_page_cache_batch(mapping, &fbatch);
         for (i = 0; i < folio_batch_count(&fbatch); i++)
             folio_unlock(fbatch.folios[i]);
         folio_batch_release(&fbatch);
         cond_resched();
     }
 
     same_folio = (lstart >> PAGE_SHIFT) == (lend >> PAGE_SHIFT);
     folio = __filemap_get_folio(mapping, lstart >> PAGE_SHIFT, FGP_LOCK, 0);
     if (folio) {
         same_folio = lend < folio_pos(folio) + folio_size(folio);
         if (!truncate_inode_partial_folio(folio, lstart, lend)) {
             start = folio->index + folio_nr_pages(folio);
             if (same_folio)
                 end = folio->index;
         }
         folio_unlock(folio);
         folio_put(folio);
         folio = NULL;
     }
 
     if (!same_folio)
         folio = __filemap_get_folio(mapping, lend >> PAGE_SHIFT,
                         FGP_LOCK, 0);
     if (folio) {
         if (!truncate_inode_partial_folio(folio, lstart, lend))
             end = folio->index;
         folio_unlock(folio);
         folio_put(folio);
     }
 
     index = start;
     while (index < end) {
         cond_resched();
         if (!find_get_entries(mapping, index, end - 1, &fbatch,
                 indices)) {
             /* If all gone from start onwards, we're done */
             if (index == start)
                 break;
             /* Otherwise restart to make sure all gone */
             index = start;
             continue;
         }
 
         for (i = 0; i < folio_batch_count(&fbatch); i++) {
             struct folio *folio = fbatch.folios[i];
 
             /* We rely upon deletion not changing page->index */
             index = indices[i];
 
             if (xa_is_value(folio))
                 continue;
 
             folio_lock(folio);
             VM_BUG_ON_FOLIO(!folio_contains(folio, index), folio);
             folio_wait_writeback(folio);
             truncate_inode_folio(mapping, folio);
             folio_unlock(folio);
             index = folio_index(folio) + folio_nr_pages(folio) - 1;
         }
         truncate_folio_batch_exceptionals(mapping, &fbatch, indices);
         folio_batch_release(&fbatch);
         index++;
     }
 }
 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_rwsem and
  * mapping->invalidate_lock.
  *
  * Note: When this function returns, there can be a page in the process of
  * deletion (inside __filemap_remove_folio()) 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);
 
 /**
  * truncate_inode_pages_final - truncate *all* pages before inode dies
  * @mapping: mapping to truncate
  *
  * Called under (and serialized by) inode->i_rwsem.
  *
  * Filesystems have to use this in the .evict_inode path to inform the
  * VM that this is the final truncate and the inode is going away.
  */
 void truncate_inode_pages_final(struct address_space *mapping)
 {
     /*
      * Page reclaim can not participate in regular inode lifetime
      * management (can't call iput()) and thus can race with the
      * inode teardown.  Tell it when the address space is exiting,
      * so that it does not install eviction information after the
      * final truncate has begun.
      */
     mapping_set_exiting(mapping);
 
     if (!mapping_empty(mapping)) {
         /*
          * As truncation uses a lockless tree lookup, cycle
          * the tree lock to make sure any ongoing tree
          * modification that does not see AS_EXITING is
          * completed before starting the final truncate.
          */
         xa_lock_irq(&mapping->i_pages);
         xa_unlock_irq(&mapping->i_pages);
     }
 
     truncate_inode_pages(mapping, 0);
 }
 EXPORT_SYMBOL(truncate_inode_pages_final);
 
 /**
  * invalidate_mapping_pagevec - 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)
  * @nr_pagevec: invalidate failed page number for caller
  *
  * This helper is similar to invalidate_mapping_pages(), except that it accounts
  * for pages that are likely on a pagevec and counts them in @nr_pagevec, which
  * will be used by the caller.
  */
 unsigned long invalidate_mapping_pagevec(struct address_space *mapping,
         pgoff_t start, pgoff_t end, unsigned long *nr_pagevec)
 {
     pgoff_t indices[PAGEVEC_SIZE];
     struct folio_batch fbatch;
     pgoff_t index = start;
     unsigned long ret;
     unsigned long count = 0;
     int i;
 
     folio_batch_init(&fbatch);
     while (find_lock_entries(mapping, index, end, &fbatch, indices)) {
         for (i = 0; i < folio_batch_count(&fbatch); i++) {
             struct folio *folio = fbatch.folios[i];
 
             /* We rely upon deletion not changing folio->index */
             index = indices[i];
 
             if (xa_is_value(folio)) {
                 count += invalidate_exceptional_entry(mapping,
                                       index,
                                       folio);
                 continue;
             }
             index += folio_nr_pages(folio) - 1;
 
             ret = mapping_evict_folio(mapping, folio);
             folio_unlock(folio);
             /*
              * Invalidation is a hint that the folio is no longer
              * of interest and try to speed up its reclaim.
              */
             if (!ret) {
                 deactivate_file_folio(folio);
                 /* It is likely on the pagevec of a remote CPU */
                 if (nr_pagevec)
                     (*nr_pagevec)++;
             }
             count += ret;
         }
         folio_batch_remove_exceptionals(&fbatch);
         folio_batch_release(&fbatch);
         cond_resched();
         index++;
     }
     return count;
 }
 
 /**
  * invalidate_mapping_pages - Invalidate all clean, unlocked cache of one inode
  * @mapping: the address_space which holds the cache to invalidate
  * @start: the offset 'from' which to invalidate
  * @end: the offset 'to' which to invalidate (inclusive)
  *
  * This function removes pages that are clean, unmapped and unlocked,
  * as well as shadow entries. It will not block on IO activity.
  *
  * If you want to remove all the pages of one inode, regardless of
  * their use and writeback state, use truncate_inode_pages().
  *
  * Return: the number of the cache entries that were invalidated
  */
 unsigned long invalidate_mapping_pages(struct address_space *mapping,
         pgoff_t start, pgoff_t end)
 {
     return invalidate_mapping_pagevec(mapping, start, end, NULL);
 }
 EXPORT_SYMBOL(invalidate_mapping_pages);
 
 /*
  * This is like invalidate_inode_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_folio2(struct address_space *mapping,
                     struct folio *folio)
 {
     if (folio->mapping != mapping)
         return 0;
 
     if (folio_has_private(folio) &&
         !filemap_release_folio(folio, GFP_KERNEL))
         return 0;
 
     spin_lock(&mapping->host->i_lock);
     xa_lock_irq(&mapping->i_pages);
     if (folio_test_dirty(folio))
         goto failed;
 
     BUG_ON(folio_has_private(folio));
     __filemap_remove_folio(folio, NULL);
     xa_unlock_irq(&mapping->i_pages);
     if (mapping_shrinkable(mapping))
         inode_add_lru(mapping->host);
     spin_unlock(&mapping->host->i_lock);
 
     filemap_free_folio(mapping, folio);
     return 1;
 failed:
     xa_unlock_irq(&mapping->i_pages);
     spin_unlock(&mapping->host->i_lock);
     return 0;
 }
 
 static int folio_launder(struct address_space *mapping, struct folio *folio)
 {
     if (!folio_test_dirty(folio))
         return 0;
     if (folio->mapping != mapping || mapping->a_ops->launder_folio == NULL)
         return 0;
     return mapping->a_ops->launder_folio(folio);
 }
 
 /**
  * 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.
  *
  * Return: -EBUSY if any pages could not be invalidated.
  */
 int invalidate_inode_pages2_range(struct address_space *mapping,
                   pgoff_t start, pgoff_t end)
 {
     pgoff_t indices[PAGEVEC_SIZE];
     struct folio_batch fbatch;
     pgoff_t index;
     int i;
     int ret = 0;
     int ret2 = 0;
     int did_range_unmap = 0;
 
     if (mapping_empty(mapping))
         return 0;
 
     folio_batch_init(&fbatch);
     index = start;
     while (find_get_entries(mapping, index, end, &fbatch, indices)) {
         for (i = 0; i < folio_batch_count(&fbatch); i++) {
             struct folio *folio = fbatch.folios[i];
 
             /* We rely upon deletion not changing folio->index */
             index = indices[i];
 
             if (xa_is_value(folio)) {
                 if (!invalidate_exceptional_entry2(mapping,
                         index, folio))
                     ret = -EBUSY;
                 continue;
             }
 
             if (!did_range_unmap && folio_mapped(folio)) {
                 /*
                  * If folio is mapped, before taking its lock,
                  * zap the rest of the file in one hit.
                  */
                 unmap_mapping_pages(mapping, index,
                         (1 + end - index), false);
                 did_range_unmap = 1;
             }
 
             folio_lock(folio);
             VM_BUG_ON_FOLIO(!folio_contains(folio, index), folio);
             if (folio->mapping != mapping) {
                 folio_unlock(folio);
                 continue;
             }
             folio_wait_writeback(folio);
 
             if (folio_mapped(folio))
                 unmap_mapping_folio(folio);
             BUG_ON(folio_mapped(folio));
 
             ret2 = folio_launder(mapping, folio);
             if (ret2 == 0) {
                 if (!invalidate_complete_folio2(mapping, folio))
                     ret2 = -EBUSY;
             }
             if (ret2 < 0)
                 ret = ret2;
             folio_unlock(folio);
         }
         folio_batch_remove_exceptionals(&fbatch);
         folio_batch_release(&fbatch);
         cond_resched();
         index++;
     }
     /*
      * For DAX we invalidate page tables after invalidating page cache.  We
      * could invalidate page tables while invalidating each entry however
      * that would be expensive. And doing range unmapping before doesn't
      * work as we have no cheap way to find whether page cache entry didn't
      * get remapped later.
      */
     if (dax_mapping(mapping)) {
         unmap_mapping_pages(mapping, start, end - start + 1, false);
     }
     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.
  *
  * Return: -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
  * @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 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 a lock serializing truncates and writes (generally
  * i_rwsem but e.g. xfs uses a different lock) and before all filesystem
  * specific block truncation has been performed.
  */
 void truncate_setsize(struct inode *inode, loff_t newsize)
 {
     loff_t oldsize = inode->i_size;
 
     i_size_write(inode, newsize);
     if (newsize > oldsize)
         pagecache_isize_extended(inode, oldsize, newsize);
     truncate_pagecache(inode, newsize);
 }
 EXPORT_SYMBOL(truncate_setsize);
 
 /**
  * pagecache_isize_extended - update pagecache after extension of i_size
  * @inode:  inode for which i_size was extended
  * @from:   original inode size
  * @to:     new inode size
  *
  * Handle extension of inode size either caused by extending truncate or by
  * write starting after current i_size. We mark the page straddling current
  * i_size RO so that page_mkwrite() is called on the nearest write access to
  * the page.  This way filesystem can be sure that page_mkwrite() is called on
  * the page before user writes to the page via mmap after the i_size has been
  * changed.
  *
  * The function must be called after i_size is updated so that page fault
  * coming after we unlock the page will already see the new i_size.
  * The function must be called while we still hold i_rwsem - this not only
  * makes sure i_size is stable but also that userspace cannot observe new
  * i_size value before we are prepared to store mmap writes at new inode size.
  */
 void pagecache_isize_extended(struct inode *inode, loff_t from, loff_t to)
 {
     int bsize = i_blocksize(inode);
     loff_t rounded_from;
     struct page *page;
     pgoff_t index;
 
     WARN_ON(to > inode->i_size);
 
     if (from >= to || bsize == PAGE_SIZE)
         return;
     /* Page straddling @from will not have any hole block created? */
     rounded_from = round_up(from, bsize);
     if (to <= rounded_from || !(rounded_from & (PAGE_SIZE - 1)))
         return;
 
     index = from >> PAGE_SHIFT;
     page = find_lock_page(inode->i_mapping, index);
     /* Page not cached? Nothing to do */
     if (!page)
         return;
     /*
      * See clear_page_dirty_for_io() for details why set_page_dirty()
      * is needed.
      */
     if (page_mkclean(page))
         set_page_dirty(page);
     unlock_page(page);
     put_page(page);
 }
 EXPORT_SYMBOL(pagecache_isize_extended);
 
 /**
  * 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.  Note that unmap_mapping_range
      * allows holelen 0 for all, and we allow lend -1 for end of file.
      */
 
     /*
      * 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);

This page was automatically generated by the 2.1.0 LXR engine. The LXR team