}
EXPORT_SYMBOL(block_page_mkwrite);
-/*
- * nobh_write_begin()'s prereads are special: the buffer_heads are freed
- * immediately, while under the page lock. So it needs a special end_io
- * handler which does not touch the bh after unlocking it.
- */
-static void end_buffer_read_nobh(struct buffer_head *bh, int uptodate)
-{
- __end_buffer_read_notouch(bh, uptodate);
-}
-
-/*
- * Attach the singly-linked list of buffers created by nobh_write_begin, to
- * the page (converting it to circular linked list and taking care of page
- * dirty races).
- */
-static void attach_nobh_buffers(struct page *page, struct buffer_head *head)
-{
- struct buffer_head *bh;
-
- BUG_ON(!PageLocked(page));
-
- spin_lock(&page->mapping->private_lock);
- bh = head;
- do {
- if (PageDirty(page))
- set_buffer_dirty(bh);
- if (!bh->b_this_page)
- bh->b_this_page = head;
- bh = bh->b_this_page;
- } while (bh != head);
- attach_page_private(page, head);
- spin_unlock(&page->mapping->private_lock);
-}
-
-/*
- * On entry, the page is fully not uptodate.
- * On exit the page is fully uptodate in the areas outside (from,to)
- * The filesystem needs to handle block truncation upon failure.
- */
-int nobh_write_begin(struct address_space *mapping, loff_t pos, unsigned len,
- struct page **pagep, void **fsdata,
- get_block_t *get_block)
-{
- struct inode *inode = mapping->host;
- const unsigned blkbits = inode->i_blkbits;
- const unsigned blocksize = 1 << blkbits;
- struct buffer_head *head, *bh;
- struct page *page;
- pgoff_t index;
- unsigned from, to;
- unsigned block_in_page;
- unsigned block_start, block_end;
- sector_t block_in_file;
- int nr_reads = 0;
- int ret = 0;
- int is_mapped_to_disk = 1;
-
- index = pos >> PAGE_SHIFT;
- from = pos & (PAGE_SIZE - 1);
- to = from + len;
-
- page = grab_cache_page_write_begin(mapping, index);
- if (!page)
- return -ENOMEM;
- *pagep = page;
- *fsdata = NULL;
-
- if (page_has_buffers(page)) {
- ret = __block_write_begin(page, pos, len, get_block);
- if (unlikely(ret))
- goto out_release;
- return ret;
- }
-
- if (PageMappedToDisk(page))
- return 0;
-
- /*
- * Allocate buffers so that we can keep track of state, and potentially
- * attach them to the page if an error occurs. In the common case of
- * no error, they will just be freed again without ever being attached
- * to the page (which is all OK, because we're under the page lock).
- *
- * Be careful: the buffer linked list is a NULL terminated one, rather
- * than the circular one we're used to.
- */
- head = alloc_page_buffers(page, blocksize, false);
- if (!head) {
- ret = -ENOMEM;
- goto out_release;
- }
-
- block_in_file = (sector_t)page->index << (PAGE_SHIFT - blkbits);
-
- /*
- * We loop across all blocks in the page, whether or not they are
- * part of the affected region. This is so we can discover if the
- * page is fully mapped-to-disk.
- */
- for (block_start = 0, block_in_page = 0, bh = head;
- block_start < PAGE_SIZE;
- block_in_page++, block_start += blocksize, bh = bh->b_this_page) {
- int create;
-
- block_end = block_start + blocksize;
- bh->b_state = 0;
- create = 1;
- if (block_start >= to)
- create = 0;
- ret = get_block(inode, block_in_file + block_in_page,
- bh, create);
- if (ret)
- goto failed;
- if (!buffer_mapped(bh))
- is_mapped_to_disk = 0;
- if (buffer_new(bh))
- clean_bdev_bh_alias(bh);
- if (PageUptodate(page)) {
- set_buffer_uptodate(bh);
- continue;
- }
- if (buffer_new(bh) || !buffer_mapped(bh)) {
- zero_user_segments(page, block_start, from,
- to, block_end);
- continue;
- }
- if (buffer_uptodate(bh))
- continue; /* reiserfs does this */
- if (block_start < from || block_end > to) {
- lock_buffer(bh);
- bh->b_end_io = end_buffer_read_nobh;
- submit_bh(REQ_OP_READ, 0, bh);
- nr_reads++;
- }
- }
-
- if (nr_reads) {
- /*
- * The page is locked, so these buffers are protected from
- * any VM or truncate activity. Hence we don't need to care
- * for the buffer_head refcounts.
- */
- for (bh = head; bh; bh = bh->b_this_page) {
- wait_on_buffer(bh);
- if (!buffer_uptodate(bh))
- ret = -EIO;
- }
- if (ret)
- goto failed;
- }
-
- if (is_mapped_to_disk)
- SetPageMappedToDisk(page);
-
- *fsdata = head; /* to be released by nobh_write_end */
-
- return 0;
-
-failed:
- BUG_ON(!ret);
- /*
- * Error recovery is a bit difficult. We need to zero out blocks that
- * were newly allocated, and dirty them to ensure they get written out.
- * Buffers need to be attached to the page at this point, otherwise
- * the handling of potential IO errors during writeout would be hard
- * (could try doing synchronous writeout, but what if that fails too?)
- */
- attach_nobh_buffers(page, head);
- page_zero_new_buffers(page, from, to);
-
-out_release:
- unlock_page(page);
- put_page(page);
- *pagep = NULL;
-
- return ret;
-}
-EXPORT_SYMBOL(nobh_write_begin);
-
-int nobh_write_end(struct file *file, struct address_space *mapping,
- loff_t pos, unsigned len, unsigned copied,
- struct page *page, void *fsdata)
-{
- struct inode *inode = page->mapping->host;
- struct buffer_head *head = fsdata;
- struct buffer_head *bh;
- BUG_ON(fsdata != NULL && page_has_buffers(page));
-
- if (unlikely(copied < len) && head)
- attach_nobh_buffers(page, head);
- if (page_has_buffers(page))
- return generic_write_end(file, mapping, pos, len,
- copied, page, fsdata);
-
- SetPageUptodate(page);
- set_page_dirty(page);
- if (pos+copied > inode->i_size) {
- i_size_write(inode, pos+copied);
- mark_inode_dirty(inode);
- }
-
- unlock_page(page);
- put_page(page);
-
- while (head) {
- bh = head;
- head = head->b_this_page;
- free_buffer_head(bh);
- }
-
- return copied;
-}
-EXPORT_SYMBOL(nobh_write_end);
-
-/*
- * nobh_writepage() - based on block_full_write_page() except
- * that it tries to operate without attaching bufferheads to
- * the page.
- */
-int nobh_writepage(struct page *page, get_block_t *get_block,
- struct writeback_control *wbc)
-{
- struct inode * const inode = page->mapping->host;
- loff_t i_size = i_size_read(inode);
- const pgoff_t end_index = i_size >> PAGE_SHIFT;
- unsigned offset;
- int ret;
-
- /* Is the page fully inside i_size? */
- if (page->index < end_index)
- goto out;
-
- /* Is the page fully outside i_size? (truncate in progress) */
- offset = i_size & (PAGE_SIZE-1);
- if (page->index >= end_index+1 || !offset) {
- unlock_page(page);
- return 0; /* don't care */
- }
-
- /*
- * The page straddles i_size. It must be zeroed out on each and every
- * writepage invocation 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."
- */
- zero_user_segment(page, offset, PAGE_SIZE);
-out:
- ret = mpage_writepage(page, get_block, wbc);
- if (ret == -EAGAIN)
- ret = __block_write_full_page(inode, page, get_block, wbc,
- end_buffer_async_write);
- return ret;
-}
-EXPORT_SYMBOL(nobh_writepage);
-
-int nobh_truncate_page(struct address_space *mapping,
- loff_t from, get_block_t *get_block)
-{
- pgoff_t index = from >> PAGE_SHIFT;
- struct inode *inode = mapping->host;
- unsigned blocksize = i_blocksize(inode);
- struct folio *folio;
- struct buffer_head map_bh;
- size_t offset;
- sector_t iblock;
- int err;
-
- /* Block boundary? Nothing to do */
- if (!(from & (blocksize - 1)))
- return 0;
-
- folio = __filemap_get_folio(mapping, index, FGP_LOCK | FGP_CREAT,
- mapping_gfp_mask(mapping));
- err = -ENOMEM;
- if (!folio)
- goto out;
-
- if (folio_buffers(folio))
- goto has_buffers;
-
- iblock = from >> inode->i_blkbits;
- map_bh.b_size = blocksize;
- map_bh.b_state = 0;
- err = get_block(inode, iblock, &map_bh, 0);
- if (err)
- goto unlock;
- /* unmapped? It's a hole - nothing to do */
- if (!buffer_mapped(&map_bh))
- goto unlock;
-
- /* Ok, it's mapped. Make sure it's up-to-date */
- if (!folio_test_uptodate(folio)) {
- err = mapping->a_ops->read_folio(NULL, folio);
- if (err) {
- folio_put(folio);
- goto out;
- }
- folio_lock(folio);
- if (!folio_test_uptodate(folio)) {
- err = -EIO;
- goto unlock;
- }
- if (folio_buffers(folio))
- goto has_buffers;
- }
- offset = offset_in_folio(folio, from);
- folio_zero_segment(folio, offset, round_up(offset, blocksize));
- folio_mark_dirty(folio);
- err = 0;
-
-unlock:
- folio_unlock(folio);
- folio_put(folio);
-out:
- return err;
-
-has_buffers:
- folio_unlock(folio);
- folio_put(folio);
- return block_truncate_page(mapping, from, get_block);
-}
-EXPORT_SYMBOL(nobh_truncate_page);
-
int block_truncate_page(struct address_space *mapping,
loff_t from, get_block_t *get_block)
{
projects / people / ms / linux.git / commitdiff
