// 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/shmem_fs.h>
#include <linux/rmap.h>
#include "internal.h"

static void clear_shadow_entries(struct address_space *mapping,
                                 unsigned long start, unsigned long max)
{
        XA_STATE(xas, &mapping->i_pages, start);
        struct folio *folio;

        /* Handled by shmem itself, or for DAX we do nothing. */
        if (shmem_mapping(mapping) || dax_mapping(mapping))
                return;

        xas_set_update(&xas, workingset_update_node);

        spin_lock(&mapping->host->i_lock);
        xas_lock_irq(&xas);

        /* Clear all shadow entries from start to max */
        xas_for_each(&xas, folio, max) {
                if (xa_is_value(folio))
                        xas_store(&xas, NULL);
        }

        xas_unlock_irq(&xas);
        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.
 * Please note that indices[] has entries in ascending order as guaranteed by
 * either find_get_entries() or find_lock_entries().
 */
static void truncate_folio_batch_exceptionals(struct address_space *mapping,
                                struct folio_batch *fbatch, pgoff_t *indices)
{
        XA_STATE(xas, &mapping->i_pages, indices[0]);
        int nr = folio_batch_count(fbatch);
        struct folio *folio;
        int i, j;

        /* Handled by shmem itself */
        if (shmem_mapping(mapping))
                return;

        for (j = 0; j < nr; j++)
                if (xa_is_value(fbatch->folios[j]))
                        break;

        if (j == nr)
                return;

        if (dax_mapping(mapping)) {
                for (i = j; i < nr; i++) {
                        if (xa_is_value(fbatch->folios[i])) {
                                /*
                                 * File systems should already have called
                                 * dax_break_layout_entry() to remove all DAX
                                 * entries while holding a lock to prevent
                                 * establishing new entries. Therefore we
                                 * shouldn't find any here.
                                 */
                                WARN_ON_ONCE(1);

                                /*
                                 * Delete the mapping so truncate_pagecache()
                                 * doesn't loop forever.
                                 */
                                dax_delete_mapping_entry(mapping, indices[i]);
                        }
                }
                goto out;
        }

        xas_set(&xas, indices[j]);
        xas_set_update(&xas, workingset_update_node);

        spin_lock(&mapping->host->i_lock);
        xas_lock_irq(&xas);

        xas_for_each(&xas, folio, indices[nr-1]) {
                if (xa_is_value(folio))
                        xas_store(&xas, NULL);
        }

        xas_unlock_irq(&xas);
        if (mapping_shrinkable(mapping))
                inode_add_lru(mapping->host);
        spin_unlock(&mapping->host->i_lock);
out:
        folio_batch_remove_exceptionals(fbatch);
}

/**
 * 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_needs_release(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);
}

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);
        size_t size = folio_size(folio);
        unsigned int offset, length;
        struct page *split_at, *split_at2;

        if (pos < start)
                offset = start - pos;
        else
                offset = 0;
        if (pos + size <= (u64)end)
                length = size - offset;
        else
                length = end + 1 - pos - offset;

        folio_wait_writeback(folio);
        if (length == size) {
                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.
         */
        if (!mapping_inaccessible(folio->mapping))
                folio_zero_range(folio, offset, length);

        if (folio_needs_release(folio))
                folio_invalidate(folio, offset, length);
        if (!folio_test_large(folio))
                return true;

        split_at = folio_page(folio, PAGE_ALIGN_DOWN(offset) / PAGE_SIZE);
        if (!try_folio_split(folio, split_at, NULL)) {
                /*
                 * try to split at offset + length to make sure folios within
                 * the range can be dropped, especially to avoid memory waste
                 * for shmem truncate
                 */
                struct folio *folio2;

                if (offset + length == size)
                        goto no_split;

                split_at2 = folio_page(folio,
                                PAGE_ALIGN_DOWN(offset + length) / PAGE_SIZE);
                folio2 = page_folio(split_at2);

                if (!folio_try_get(folio2))
                        goto no_split;

                if (!folio_test_large(folio2))
                        goto out;

                if (!folio_trylock(folio2))
                        goto out;

                /*
                 * make sure folio2 is large and does not change its mapping.
                 * Its split result does not matter here.
                 */
                if (folio_test_large(folio2) &&
                    folio2->mapping == folio->mapping)
                        try_folio_split(folio2, split_at2, NULL);

                folio_unlock(folio2);
out:
                folio_put(folio2);
no_split:
                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_folio(struct address_space *mapping,
                struct folio *folio)
{
        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, folio);
}
EXPORT_SYMBOL(generic_error_remove_folio);

/**
 * mapping_evict_folio() - Remove an unused folio from the page-cache.
 * @mapping: The mapping this folio belongs to.
 * @folio: The folio to remove.
 *
 * Safely remove one folio from the page cache.
 * It only drops clean, unused folios.
 *
 * Context: Folio must be locked.
 * Return: The number of pages successfully removed.
 */
long mapping_evict_folio(struct address_space *mapping, struct folio *folio)
{
        /* The page may have been truncated before it was locked */
        if (!mapping)
                return 0;
        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 (!filemap_release_folio(folio, 0))
                return 0;

        return remove_mapping(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)) {
                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 (!IS_ERR(folio)) {
                same_folio = lend < folio_pos(folio) + folio_size(folio);
                if (!truncate_inode_partial_folio(folio, lstart, lend)) {
                        start = folio_next_index(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 (!IS_ERR(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 folio->index */

                        if (xa_is_value(folio))
                                continue;

                        folio_lock(folio);
                        VM_BUG_ON_FOLIO(!folio_contains(folio, indices[i]), folio);
                        folio_wait_writeback(folio);
                        truncate_inode_folio(mapping, folio);
                        folio_unlock(folio);
                }
                truncate_folio_batch_exceptionals(mapping, &fbatch, indices);
                folio_batch_release(&fbatch);
        }
}
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);

/**
 * mapping_try_invalidate - Invalidate all the evictable folios of one inode
 * @mapping: the address_space which holds the folios to invalidate
 * @start: the offset 'from' which to invalidate
 * @end: the offset 'to' which to invalidate (inclusive)
 * @nr_failed: How many folio invalidations failed
 *
 * This function is similar to invalidate_mapping_pages(), except that it
 * returns the number of folios which could not be evicted in @nr_failed.
 */
unsigned long mapping_try_invalidate(struct address_space *mapping,
                pgoff_t start, pgoff_t end, unsigned long *nr_failed)
{
        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)) {
                bool xa_has_values = false;
                int nr = folio_batch_count(&fbatch);

                for (i = 0; i < nr; i++) {
                        struct folio *folio = fbatch.folios[i];

                        /* We rely upon deletion not changing folio->index */

                        if (xa_is_value(folio)) {
                                xa_has_values = true;
                                count++;
                                continue;
                        }

                        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);
                                /* Likely in the lru cache of a remote CPU */
                                if (nr_failed)
                                        (*nr_failed)++;
                        }
                        count += ret;
                }

                if (xa_has_values)
                        clear_shadow_entries(mapping, indices[0], indices[nr-1]);

                folio_batch_remove_exceptionals(&fbatch);
                folio_batch_release(&fbatch);
                cond_resched();
        }
        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 indices that had their contents invalidated
 */
unsigned long invalidate_mapping_pages(struct address_space *mapping,
                pgoff_t start, pgoff_t end)
{
        return mapping_try_invalidate(mapping, start, end, NULL);
}
EXPORT_SYMBOL(invalidate_mapping_pages);

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);
}

/*
 * This is like mapping_evict_folio(), except it ignores the folio's
 * refcount.  We do this because invalidate_inode_pages2() needs stronger
 * invalidation guarantees, and cannot afford to leave folios behind because
 * shrink_folio_list() has a temp ref on them, or because they're transiently
 * sitting in the folio_add_lru() caches.
 */
int folio_unmap_invalidate(struct address_space *mapping, struct folio *folio,
                           gfp_t gfp)
{
        int ret;

        VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);

        if (folio_mapped(folio))
                unmap_mapping_folio(folio);
        BUG_ON(folio_mapped(folio));

        ret = folio_launder(mapping, folio);
        if (ret)
                return ret;
        if (folio->mapping != mapping)
                return -EBUSY;
        if (!filemap_release_folio(folio, gfp))
                return -EBUSY;

        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 -EBUSY;
}

/**
 * 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)) {
                bool xa_has_values = false;
                int nr = folio_batch_count(&fbatch);

                for (i = 0; i < nr; i++) {
                        struct folio *folio = fbatch.folios[i];

                        /* We rely upon deletion not changing folio->index */

                        if (xa_is_value(folio)) {
                                xa_has_values = true;
                                if (dax_mapping(mapping) &&
                                    !dax_invalidate_mapping_entry_sync(mapping, indices[i]))
                                        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, indices[i],
                                                (1 + end - indices[i]), false);
                                did_range_unmap = 1;
                        }

                        folio_lock(folio);
                        if (unlikely(folio->mapping != mapping)) {
                                folio_unlock(folio);
                                continue;
                        }
                        VM_BUG_ON_FOLIO(!folio_contains(folio, indices[i]), folio);
                        folio_wait_writeback(folio);
                        ret2 = folio_unmap_invalidate(mapping, folio, GFP_KERNEL);
                        if (ret2 < 0)
                                ret = ret2;
                        folio_unlock(folio);
                }

                if (xa_has_values)
                        clear_shadow_entries(mapping, indices[0], indices[nr-1]);

                folio_batch_remove_exceptionals(&fbatch);
                folio_batch_release(&fbatch);
                cond_resched();
        }
        /*
         * 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 first
 * write access to the page.  The filesystem will update its per-block
 * information 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 folio 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 folio *folio;

        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;

        folio = filemap_lock_folio(inode->i_mapping, from / PAGE_SIZE);
        /* Folio not cached? Nothing to do */
        if (IS_ERR(folio))
                return;
        /*
         * See folio_clear_dirty_for_io() for details why folio_mark_dirty()
         * is needed.
         */
        if (folio_mkclean(folio))
                folio_mark_dirty(folio);

        /*
         * The post-eof range of the folio must be zeroed before it is exposed
         * to the file. Writeback normally does this, but since i_size has been
         * increased we handle it here.
         */
        if (folio_test_dirty(folio)) {
                unsigned int offset, end;

                offset = from - folio_pos(folio);
                end = min_t(unsigned int, to - folio_pos(folio),
                            folio_size(folio));
                folio_zero_segment(folio, offset, end);
        }

        folio_unlock(folio);
        folio_put(folio);
}
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);