Linux-2.6.12-rc2v2.6.12-rc2

Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!

1 files changed, 772 insertions, 0 deletions

diff --git a/fs/mpage.c b/fs/mpage.c
new file mode 100644
index 000000000000..e7d8d1a77606
--- /dev/null
+++ b/fs/mpage.c
@@ -0,0 +1,772 @@
+/*
+ * fs/mpage.c
+ *
+ * Copyright (C) 2002, Linus Torvalds.
+ *
+ * Contains functions related to preparing and submitting BIOs which contain
+ * multiple pagecache pages.
+ *
+ * 15May2002    akpm@zip.com.au
+ *              Initial version
+ * 27Jun2002    axboe@suse.de
+ *              use bio_add_page() to build bio's just the right size
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/mm.h>
+#include <linux/kdev_t.h>
+#include <linux/bio.h>
+#include <linux/fs.h>
+#include <linux/buffer_head.h>
+#include <linux/blkdev.h>
+#include <linux/highmem.h>
+#include <linux/prefetch.h>
+#include <linux/mpage.h>
+#include <linux/writeback.h>
+#include <linux/backing-dev.h>
+#include <linux/pagevec.h>
+
+/*
+ * I/O completion handler for multipage BIOs.
+ *
+ * The mpage code never puts partial pages into a BIO (except for end-of-file).
+ * If a page does not map to a contiguous run of blocks then it simply falls
+ * back to block_read_full_page().
+ *
+ * Why is this?  If a page's completion depends on a number of different BIOs
+ * which can complete in any order (or at the same time) then determining the
+ * status of that page is hard.  See end_buffer_async_read() for the details.
+ * There is no point in duplicating all that complexity.
+ */
+static int mpage_end_io_read(struct bio *bio, unsigned int bytes_done, int err)
+{
+        const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
+        struct bio_vec *bvec = bio->bi_io_vec + bio->bi_vcnt - 1;
+
+        if (bio->bi_size)
+                return 1;
+
+        do {
+                struct page *page = bvec->bv_page;
+
+                if (--bvec >= bio->bi_io_vec)
+                        prefetchw(&bvec->bv_page->flags);
+
+                if (uptodate) {
+                        SetPageUptodate(page);
+                } else {
+                        ClearPageUptodate(page);
+                        SetPageError(page);
+                }
+                unlock_page(page);
+        } while (bvec >= bio->bi_io_vec);
+        bio_put(bio);
+        return 0;
+}
+
+static int mpage_end_io_write(struct bio *bio, unsigned int bytes_done, int err)
+{
+        const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
+        struct bio_vec *bvec = bio->bi_io_vec + bio->bi_vcnt - 1;
+
+        if (bio->bi_size)
+                return 1;
+
+        do {
+                struct page *page = bvec->bv_page;
+
+                if (--bvec >= bio->bi_io_vec)
+                        prefetchw(&bvec->bv_page->flags);
+
+                if (!uptodate)
+                        SetPageError(page);
+                end_page_writeback(page);
+        } while (bvec >= bio->bi_io_vec);
+        bio_put(bio);
+        return 0;
+}
+
+struct bio *mpage_bio_submit(int rw, struct bio *bio)
+{
+        bio->bi_end_io = mpage_end_io_read;
+        if (rw == WRITE)
+                bio->bi_end_io = mpage_end_io_write;
+        submit_bio(rw, bio);
+        return NULL;
+}
+
+static struct bio *
+mpage_alloc(struct block_device *bdev,
+                sector_t first_sector, int nr_vecs,
+                unsigned int __nocast gfp_flags)
+{
+        struct bio *bio;
+
+        bio = bio_alloc(gfp_flags, nr_vecs);
+
+        if (bio == NULL && (current->flags & PF_MEMALLOC)) {
+                while (!bio && (nr_vecs /= 2))
+                        bio = bio_alloc(gfp_flags, nr_vecs);
+        }
+
+        if (bio) {
+                bio->bi_bdev = bdev;
+                bio->bi_sector = first_sector;
+        }
+        return bio;
+}
+
+/*
+ * support function for mpage_readpages.  The fs supplied get_block might
+ * return an up to date buffer.  This is used to map that buffer into
+ * the page, which allows readpage to avoid triggering a duplicate call
+ * to get_block.
+ *
+ * The idea is to avoid adding buffers to pages that don't already have
+ * them.  So when the buffer is up to date and the page size == block size,
+ * this marks the page up to date instead of adding new buffers.
+ */
+static void 
+map_buffer_to_page(struct page *page, struct buffer_head *bh, int page_block) 
+{
+        struct inode *inode = page->mapping->host;
+        struct buffer_head *page_bh, *head;
+        int block = 0;
+
+        if (!page_has_buffers(page)) {
+                /*
+                 * don't make any buffers if there is only one buffer on
+                 * the page and the page just needs to be set up to date
+                 */
+                if (inode->i_blkbits == PAGE_CACHE_SHIFT && 
+                    buffer_uptodate(bh)) {
+                        SetPageUptodate(page);    
+                        return;
+                }
+                create_empty_buffers(page, 1 << inode->i_blkbits, 0);
+        }
+        head = page_buffers(page);
+        page_bh = head;
+        do {
+                if (block == page_block) {
+                        page_bh->b_state = bh->b_state;
+                        page_bh->b_bdev = bh->b_bdev;
+                        page_bh->b_blocknr = bh->b_blocknr;
+                        break;
+                }
+                page_bh = page_bh->b_this_page;
+                block++;
+        } while (page_bh != head);
+}
+
+/**
+ * mpage_readpages - populate an address space with some pages, and
+ *                       start reads against them.
+ *
+ * @mapping: the address_space
+ * @pages: The address of a list_head which contains the target pages.  These
+ *   pages have their ->index populated and are otherwise uninitialised.
+ *
+ *   The page at @pages->prev has the lowest file offset, and reads should be
+ *   issued in @pages->prev to @pages->next order.
+ *
+ * @nr_pages: The number of pages at *@pages
+ * @get_block: The filesystem's block mapper function.
+ *
+ * This function walks the pages and the blocks within each page, building and
+ * emitting large BIOs.
+ *
+ * If anything unusual happens, such as:
+ *
+ * - encountering a page which has buffers
+ * - encountering a page which has a non-hole after a hole
+ * - encountering a page with non-contiguous blocks
+ *
+ * then this code just gives up and calls the buffer_head-based read function.
+ * It does handle a page which has holes at the end - that is a common case:
+ * the end-of-file on blocksize < PAGE_CACHE_SIZE setups.
+ *
+ * BH_Boundary explanation:
+ *
+ * There is a problem.  The mpage read code assembles several pages, gets all
+ * their disk mappings, and then submits them all.  That's fine, but obtaining
+ * the disk mappings may require I/O.  Reads of indirect blocks, for example.
+ *
+ * So an mpage read of the first 16 blocks of an ext2 file will cause I/O to be
+ * submitted in the following order:
+ *      12 0 1 2 3 4 5 6 7 8 9 10 11 13 14 15 16
+ * because the indirect block has to be read to get the mappings of blocks
+ * 13,14,15,16.  Obviously, this impacts performance.
+ * 
+ * So what we do it to allow the filesystem's get_block() function to set
+ * BH_Boundary when it maps block 11.  BH_Boundary says: mapping of the block
+ * after this one will require I/O against a block which is probably close to
+ * this one.  So you should push what I/O you have currently accumulated.
+ *
+ * This all causes the disk requests to be issued in the correct order.
+ */
+static struct bio *
+do_mpage_readpage(struct bio *bio, struct page *page, unsigned nr_pages,
+                        sector_t *last_block_in_bio, get_block_t get_block)
+{
+        struct inode *inode = page->mapping->host;
+        const unsigned blkbits = inode->i_blkbits;
+        const unsigned blocks_per_page = PAGE_CACHE_SIZE >> blkbits;
+        const unsigned blocksize = 1 << blkbits;
+        sector_t block_in_file;
+        sector_t last_block;
+        sector_t blocks[MAX_BUF_PER_PAGE];
+        unsigned page_block;
+        unsigned first_hole = blocks_per_page;
+        struct block_device *bdev = NULL;
+        struct buffer_head bh;
+        int length;
+        int fully_mapped = 1;
+
+        if (page_has_buffers(page))
+                goto confused;
+
+        block_in_file = page->index << (PAGE_CACHE_SHIFT - blkbits);
+        last_block = (i_size_read(inode) + blocksize - 1) >> blkbits;
+
+        bh.b_page = page;
+        for (page_block = 0; page_block < blocks_per_page;
+                                page_block++, block_in_file++) {
+                bh.b_state = 0;
+                if (block_in_file < last_block) {
+                        if (get_block(inode, block_in_file, &bh, 0))
+                                goto confused;
+                }
+
+                if (!buffer_mapped(&bh)) {
+                        fully_mapped = 0;
+                        if (first_hole == blocks_per_page)
+                                first_hole = page_block;
+                        continue;
+                }
+
+                /* some filesystems will copy data into the page during
+                 * the get_block call, in which case we don't want to
+                 * read it again.  map_buffer_to_page copies the data
+                 * we just collected from get_block into the page's buffers
+                 * so readpage doesn't have to repeat the get_block call
+                 */
+                if (buffer_uptodate(&bh)) {
+                        map_buffer_to_page(page, &bh, page_block);
+                        goto confused;
+                }
+        
+                if (first_hole != blocks_per_page)
+                        goto confused;          /* hole -> non-hole */
+
+                /* Contiguous blocks? */
+                if (page_block && blocks[page_block-1] != bh.b_blocknr-1)
+                        goto confused;
+                blocks[page_block] = bh.b_blocknr;
+                bdev = bh.b_bdev;
+        }
+
+        if (first_hole != blocks_per_page) {
+                char *kaddr = kmap_atomic(page, KM_USER0);
+                memset(kaddr + (first_hole << blkbits), 0,
+                                PAGE_CACHE_SIZE - (first_hole << blkbits));
+                flush_dcache_page(page);
+                kunmap_atomic(kaddr, KM_USER0);
+                if (first_hole == 0) {
+                        SetPageUptodate(page);
+                        unlock_page(page);
+                        goto out;
+                }
+        } else if (fully_mapped) {
+                SetPageMappedToDisk(page);
+        }
+
+        /*
+         * This page will go to BIO.  Do we need to send this BIO off first?
+         */
+        if (bio && (*last_block_in_bio != blocks[0] - 1))
+                bio = mpage_bio_submit(READ, bio);
+
+alloc_new:
+        if (bio == NULL) {
+                bio = mpage_alloc(bdev, blocks[0] << (blkbits - 9),
+                                min_t(int, nr_pages, bio_get_nr_vecs(bdev)),
+                                GFP_KERNEL);
+                if (bio == NULL)
+                        goto confused;
+        }
+
+        length = first_hole << blkbits;
+        if (bio_add_page(bio, page, length, 0) < length) {
+                bio = mpage_bio_submit(READ, bio);
+                goto alloc_new;
+        }
+
+        if (buffer_boundary(&bh) || (first_hole != blocks_per_page))
+                bio = mpage_bio_submit(READ, bio);
+        else
+                *last_block_in_bio = blocks[blocks_per_page - 1];
+out:
+        return bio;
+
+confused:
+        if (bio)
+                bio = mpage_bio_submit(READ, bio);
+        if (!PageUptodate(page))
+                block_read_full_page(page, get_block);
+        else
+                unlock_page(page);
+        goto out;
+}
+
+int
+mpage_readpages(struct address_space *mapping, struct list_head *pages,
+                                unsigned nr_pages, get_block_t get_block)
+{
+        struct bio *bio = NULL;
+        unsigned page_idx;
+        sector_t last_block_in_bio = 0;
+        struct pagevec lru_pvec;
+
+        pagevec_init(&lru_pvec, 0);
+        for (page_idx = 0; page_idx < nr_pages; page_idx++) {
+                struct page *page = list_entry(pages->prev, struct page, lru);
+
+                prefetchw(&page->flags);
+                list_del(&page->lru);
+                if (!add_to_page_cache(page, mapping,
+                                        page->index, GFP_KERNEL)) {
+                        bio = do_mpage_readpage(bio, page,
+                                        nr_pages - page_idx,
+                                        &last_block_in_bio, get_block);
+                        if (!pagevec_add(&lru_pvec, page))
+                                __pagevec_lru_add(&lru_pvec);
+                } else {
+                        page_cache_release(page);
+                }
+        }
+        pagevec_lru_add(&lru_pvec);
+        BUG_ON(!list_empty(pages));
+        if (bio)
+                mpage_bio_submit(READ, bio);
+        return 0;
+}
+EXPORT_SYMBOL(mpage_readpages);
+
+/*
+ * This isn't called much at all
+ */
+int mpage_readpage(struct page *page, get_block_t get_block)
+{
+        struct bio *bio = NULL;
+        sector_t last_block_in_bio = 0;
+
+        bio = do_mpage_readpage(bio, page, 1,
+                        &last_block_in_bio, get_block);
+        if (bio)
+                mpage_bio_submit(READ, bio);
+        return 0;
+}
+EXPORT_SYMBOL(mpage_readpage);
+
+/*
+ * Writing is not so simple.
+ *
+ * If the page has buffers then they will be used for obtaining the disk
+ * mapping.  We only support pages which are fully mapped-and-dirty, with a
+ * special case for pages which are unmapped at the end: end-of-file.
+ *
+ * If the page has no buffers (preferred) then the page is mapped here.
+ *
+ * If all blocks are found to be contiguous then the page can go into the
+ * BIO.  Otherwise fall back to the mapping's writepage().
+ * 
+ * FIXME: This code wants an estimate of how many pages are still to be
+ * written, so it can intelligently allocate a suitably-sized BIO.  For now,
+ * just allocate full-size (16-page) BIOs.
+ */
+static struct bio *
+__mpage_writepage(struct bio *bio, struct page *page, get_block_t get_block,
+        sector_t *last_block_in_bio, int *ret, struct writeback_control *wbc,
+        writepage_t writepage_fn)
+{
+        struct address_space *mapping = page->mapping;
+        struct inode *inode = page->mapping->host;
+        const unsigned blkbits = inode->i_blkbits;
+        unsigned long end_index;
+        const unsigned blocks_per_page = PAGE_CACHE_SIZE >> blkbits;
+        sector_t last_block;
+        sector_t block_in_file;
+        sector_t blocks[MAX_BUF_PER_PAGE];
+        unsigned page_block;
+        unsigned first_unmapped = blocks_per_page;
+        struct block_device *bdev = NULL;
+        int boundary = 0;
+        sector_t boundary_block = 0;
+        struct block_device *boundary_bdev = NULL;
+        int length;
+        struct buffer_head map_bh;
+        loff_t i_size = i_size_read(inode);
+
+        if (page_has_buffers(page)) {
+                struct buffer_head *head = page_buffers(page);
+                struct buffer_head *bh = head;
+
+                /* If they're all mapped and dirty, do it */
+                page_block = 0;
+                do {
+                        BUG_ON(buffer_locked(bh));
+                        if (!buffer_mapped(bh)) {
+                                /*
+                                 * unmapped dirty buffers are created by
+                                 * __set_page_dirty_buffers -> mmapped data
+                                 */
+                                if (buffer_dirty(bh))
+                                        goto confused;
+                                if (first_unmapped == blocks_per_page)
+                                        first_unmapped = page_block;
+                                continue;
+                        }
+
+                        if (first_unmapped != blocks_per_page)
+                                goto confused;  /* hole -> non-hole */
+
+                        if (!buffer_dirty(bh) || !buffer_uptodate(bh))
+                                goto confused;
+                        if (page_block) {
+                                if (bh->b_blocknr != blocks[page_block-1] + 1)
+                                        goto confused;
+                        }
+                        blocks[page_block++] = bh->b_blocknr;
+                        boundary = buffer_boundary(bh);
+                        if (boundary) {
+                                boundary_block = bh->b_blocknr;
+                                boundary_bdev = bh->b_bdev;
+                        }
+                        bdev = bh->b_bdev;
+                } while ((bh = bh->b_this_page) != head);
+
+                if (first_unmapped)
+                        goto page_is_mapped;
+
+                /*
+                 * Page has buffers, but they are all unmapped. The page was
+                 * created by pagein or read over a hole which was handled by
+                 * block_read_full_page().  If this address_space is also
+                 * using mpage_readpages then this can rarely happen.
+                 */
+                goto confused;
+        }
+
+        /*
+         * The page has no buffers: map it to disk
+         */
+        BUG_ON(!PageUptodate(page));
+        block_in_file = page->index << (PAGE_CACHE_SHIFT - blkbits);
+        last_block = (i_size - 1) >> blkbits;
+        map_bh.b_page = page;
+        for (page_block = 0; page_block < blocks_per_page; ) {
+
+                map_bh.b_state = 0;
+                if (get_block(inode, block_in_file, &map_bh, 1))
+                        goto confused;
+                if (buffer_new(&map_bh))
+                        unmap_underlying_metadata(map_bh.b_bdev,
+                                                map_bh.b_blocknr);
+                if (buffer_boundary(&map_bh)) {
+                        boundary_block = map_bh.b_blocknr;
+                        boundary_bdev = map_bh.b_bdev;
+                }
+                if (page_block) {
+                        if (map_bh.b_blocknr != blocks[page_block-1] + 1)
+                                goto confused;
+                }
+                blocks[page_block++] = map_bh.b_blocknr;
+                boundary = buffer_boundary(&map_bh);
+                bdev = map_bh.b_bdev;
+                if (block_in_file == last_block)
+                        break;
+                block_in_file++;
+        }
+        BUG_ON(page_block == 0);
+
+        first_unmapped = page_block;
+
+page_is_mapped:
+        end_index = i_size >> PAGE_CACHE_SHIFT;
+        if (page->index >= end_index) {
+                /*
+                 * The page straddles i_size.  It must be zeroed out on each
+                 * and every writepage invokation because it may be mmapped.
+                 * "A file is mapped in multiples of the page size.  For a file
+                 * that is not a multiple of the page size, the remaining memory
+                 * is zeroed when mapped, and writes to that region are not
+                 * written out to the file."
+                 */
+                unsigned offset = i_size & (PAGE_CACHE_SIZE - 1);
+                char *kaddr;
+
+                if (page->index > end_index || !offset)
+                        goto confused;
+                kaddr = kmap_atomic(page, KM_USER0);
+                memset(kaddr + offset, 0, PAGE_CACHE_SIZE - offset);
+                flush_dcache_page(page);
+                kunmap_atomic(kaddr, KM_USER0);
+        }
+
+        /*
+         * This page will go to BIO.  Do we need to send this BIO off first?
+         */
+        if (bio && *last_block_in_bio != blocks[0] - 1)
+                bio = mpage_bio_submit(WRITE, bio);
+
+alloc_new:
+        if (bio == NULL) {
+                bio = mpage_alloc(bdev, blocks[0] << (blkbits - 9),
+                                bio_get_nr_vecs(bdev), GFP_NOFS|__GFP_HIGH);
+                if (bio == NULL)
+                        goto confused;
+        }
+
+        /*
+         * Must try to add the page before marking the buffer clean or
+         * the confused fail path above (OOM) will be very confused when
+         * it finds all bh marked clean (i.e. it will not write anything)
+         */
+        length = first_unmapped << blkbits;
+        if (bio_add_page(bio, page, length, 0) < length) {
+                bio = mpage_bio_submit(WRITE, bio);
+                goto alloc_new;
+        }
+
+        /*
+         * OK, we have our BIO, so we can now mark the buffers clean.  Make
+         * sure to only clean buffers which we know we'll be writing.
+         */
+        if (page_has_buffers(page)) {
+                struct buffer_head *head = page_buffers(page);
+                struct buffer_head *bh = head;
+                unsigned buffer_counter = 0;
+
+                do {
+                        if (buffer_counter++ == first_unmapped)
+                                break;
+                        clear_buffer_dirty(bh);
+                        bh = bh->b_this_page;
+                } while (bh != head);
+
+                /*
+                 * we cannot drop the bh if the page is not uptodate
+                 * or a concurrent readpage would fail to serialize with the bh
+                 * and it would read from disk before we reach the platter.
+                 */
+                if (buffer_heads_over_limit && PageUptodate(page))
+                        try_to_free_buffers(page);
+        }
+
+        BUG_ON(PageWriteback(page));
+        set_page_writeback(page);
+        unlock_page(page);
+        if (boundary || (first_unmapped != blocks_per_page)) {
+                bio = mpage_bio_submit(WRITE, bio);
+                if (boundary_block) {
+                        write_boundary_block(boundary_bdev,
+                                        boundary_block, 1 << blkbits);
+                }
+        } else {
+                *last_block_in_bio = blocks[blocks_per_page - 1];
+        }
+        goto out;
+
+confused:
+        if (bio)
+                bio = mpage_bio_submit(WRITE, bio);
+
+        if (writepage_fn) {
+                *ret = (*writepage_fn)(page, wbc);
+        } else {
+                *ret = -EAGAIN;
+                goto out;
+        }
+        /*
+         * The caller has a ref on the inode, so *mapping is stable
+         */
+        if (*ret) {
+                if (*ret == -ENOSPC)
+                        set_bit(AS_ENOSPC, &mapping->flags);
+                else
+                        set_bit(AS_EIO, &mapping->flags);
+        }
+out:
+        return bio;
+}
+
+/**
+ * mpage_writepages - walk the list of dirty pages of the given
+ * address space and writepage() all of them.
+ * 
+ * @mapping: address space structure to write
+ * @wbc: subtract the number of written pages from *@wbc->nr_to_write
+ * @get_block: the filesystem's block mapper function.
+ *             If this is NULL then use a_ops->writepage.  Otherwise, go
+ *             direct-to-BIO.
+ *
+ * This is a library function, which implements the writepages()
+ * address_space_operation.
+ *
+ * If a page is already under I/O, generic_writepages() skips it, even
+ * if it's dirty.  This is desirable behaviour for memory-cleaning writeback,
+ * but it is INCORRECT for data-integrity system calls such as fsync().  fsync()
+ * and msync() need to guarantee that all the data which was dirty at the time
+ * the call was made get new I/O started against them.  If wbc->sync_mode is
+ * WB_SYNC_ALL then we were called for data integrity and we must wait for
+ * existing IO to complete.
+ */
+int
+mpage_writepages(struct address_space *mapping,
+                struct writeback_control *wbc, get_block_t get_block)
+{
+        return __mpage_writepages(mapping, wbc, get_block,
+                mapping->a_ops->writepage);
+}
+
+int
+__mpage_writepages(struct address_space *mapping,
+                struct writeback_control *wbc, get_block_t get_block,
+                writepage_t writepage_fn)
+{
+        struct backing_dev_info *bdi = mapping->backing_dev_info;
+        struct bio *bio = NULL;
+        sector_t last_block_in_bio = 0;
+        int ret = 0;
+        int done = 0;
+        int (*writepage)(struct page *page, struct writeback_control *wbc);
+        struct pagevec pvec;
+        int nr_pages;
+        pgoff_t index;
+        pgoff_t end = -1;               /* Inclusive */
+        int scanned = 0;
+        int is_range = 0;
+
+        if (wbc->nonblocking && bdi_write_congested(bdi)) {
+                wbc->encountered_congestion = 1;
+                return 0;
+        }
+
+        writepage = NULL;
+        if (get_block == NULL)
+                writepage = mapping->a_ops->writepage;
+
+        pagevec_init(&pvec, 0);
+        if (wbc->sync_mode == WB_SYNC_NONE) {
+                index = mapping->writeback_index; /* Start from prev offset */
+        } else {
+                index = 0;                        /* whole-file sweep */
+                scanned = 1;
+        }
+        if (wbc->start || wbc->end) {
+                index = wbc->start >> PAGE_CACHE_SHIFT;
+                end = wbc->end >> PAGE_CACHE_SHIFT;
+                is_range = 1;
+                scanned = 1;
+        }
+retry:
+        while (!done && (index <= end) &&
+                        (nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
+                        PAGECACHE_TAG_DIRTY,
+                        min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1))) {
+                unsigned i;
+
+                scanned = 1;
+                for (i = 0; i < nr_pages; i++) {
+                        struct page *page = pvec.pages[i];
+
+                        /*
+                         * At this point we hold neither mapping->tree_lock nor
+                         * lock on the page itself: the page may be truncated or
+                         * invalidated (changing page->mapping to NULL), or even
+                         * swizzled back from swapper_space to tmpfs file
+                         * mapping
+                         */
+
+                        lock_page(page);
+
+                        if (unlikely(page->mapping != mapping)) {
+                                unlock_page(page);
+                                continue;
+                        }
+
+                        if (unlikely(is_range) && page->index > end) {
+                                done = 1;
+                                unlock_page(page);
+                                continue;
+                        }
+
+                        if (wbc->sync_mode != WB_SYNC_NONE)
+                                wait_on_page_writeback(page);
+
+                        if (PageWriteback(page) ||
+                                        !clear_page_dirty_for_io(page)) {
+                                unlock_page(page);
+                                continue;
+                        }
+
+                        if (writepage) {
+                                ret = (*writepage)(page, wbc);
+                                if (ret) {
+                                        if (ret == -ENOSPC)
+                                                set_bit(AS_ENOSPC,
+                                                        &mapping->flags);
+                                        else
+                                                set_bit(AS_EIO,
+                                                        &mapping->flags);
+                                }
+                        } else {
+                                bio = __mpage_writepage(bio, page, get_block,
+                                                &last_block_in_bio, &ret, wbc,
+                                                writepage_fn);
+                        }
+                        if (ret || (--(wbc->nr_to_write) <= 0))
+                                done = 1;
+                        if (wbc->nonblocking && bdi_write_congested(bdi)) {
+                                wbc->encountered_congestion = 1;
+                                done = 1;
+                        }
+                }
+                pagevec_release(&pvec);
+                cond_resched();
+        }
+        if (!scanned && !done) {
+                /*
+                 * We hit the last page and there is more work to be done: wrap
+                 * back to the start of the file
+                 */
+                scanned = 1;
+                index = 0;
+                goto retry;
+        }
+        if (!is_range)
+                mapping->writeback_index = index;
+        if (bio)
+                mpage_bio_submit(WRITE, bio);
+        return ret;
+}
+EXPORT_SYMBOL(mpage_writepages);
+EXPORT_SYMBOL(__mpage_writepages);
+
+int mpage_writepage(struct page *page, get_block_t get_block,
+        struct writeback_control *wbc)
+{
+        int ret = 0;
+        struct bio *bio;
+        sector_t last_block_in_bio = 0;
+
+        bio = __mpage_writepage(NULL, page, get_block,
+                        &last_block_in_bio, &ret, wbc, NULL);
+        if (bio)
+                mpage_bio_submit(WRITE, bio);
+
+        return ret;
+}
+EXPORT_SYMBOL(mpage_writepage);