Commit e97d70a5 authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Chandan Babu R
Browse files

xfs: use shmem_get_folio in in xfile_load 



Switch to using shmem_get_folio in xfile_load instead of using
shmem_read_mapping_page_gfp.  This gets us support for large folios
and also optimized reading from unallocated space, as
shmem_get_folio with SGP_READ won't allocate a page for them just
to zero the content.

Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatar"Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: default avatarChandan Babu R <chandanbabu@kernel.org>
parent fd2634e2

fs/xfs/scrub/xfile.c

+26 −35
Original line number Diff line number Diff line
@@ -34,13 +34,6 @@ 
 * xfiles assume that the caller will handle all required concurrency

 * management; standard vfs locks (freezer and inode) are not taken.  Reads

 * and writes are satisfied directly from the page cache.

 *

 * NOTE: The current shmemfs implementation has a quirk that in-kernel reads

 * of a hole cause a page to be mapped into the file.  If you are going to

 * create a sparse xfile, please be careful about reading from uninitialized

 * parts of the file.  These pages are !Uptodate and will eventually be

 * reclaimed if not written, but in the short term this boosts memory

 * consumption.

 */



/*
@@ -118,10 +111,7 @@ xfile_load( 
	loff_t			pos)

{

	struct inode		*inode = file_inode(xf->file);

	struct address_space	*mapping = inode->i_mapping;

	struct page		*page = NULL;

	unsigned int		pflags;

	int			error = 0;



	if (count > MAX_RW_COUNT)

		return -ENOMEM;
@@ -132,43 +122,44 @@ xfile_load( 


	pflags = memalloc_nofs_save();

	while (count > 0) {

		struct folio	*folio;

		unsigned int	len;

		unsigned int	offset;



		len = min_t(ssize_t, count, PAGE_SIZE - offset_in_page(pos));



		if (shmem_get_folio(inode, pos >> PAGE_SHIFT, &folio,

				SGP_READ) < 0)

			break;

		if (!folio) {

			/*

		 * In-kernel reads of a shmem file cause it to allocate a page

		 * if the mapping shows a hole.  Therefore, if we hit ENOMEM

		 * we can continue by zeroing the caller's buffer.

			 * No data stored at this offset, just zero the output

			 * buffer until the next page boundary.

			 */

		page = shmem_read_mapping_page_gfp(mapping, pos >> PAGE_SHIFT,

				__GFP_NOWARN);

		if (IS_ERR(page)) {

			error = PTR_ERR(page);

			if (error != -ENOMEM) {

				error = -ENOMEM;

				break;

			}



			len = min_t(ssize_t, count,

				PAGE_SIZE - offset_in_page(pos));

			memset(buf, 0, len);

			goto advance;

		} else {

			if (filemap_check_wb_err(inode->i_mapping, 0)) {

				folio_unlock(folio);

				folio_put(folio);

				break;

			}



		/*

		 * xfile pages must never be mapped into userspace, so

		 * we skip the dcache flush.

		 */

		memcpy(buf, page_address(page) + offset_in_page(pos), len);

		put_page(page);

			offset = offset_in_folio(folio, pos);

			len = min_t(ssize_t, count, folio_size(folio) - offset);

			memcpy(buf, folio_address(folio) + offset, len);



advance:

			folio_unlock(folio);

			folio_put(folio);

		}

		count -= len;

		pos += len;

		buf += len;

	}

	memalloc_nofs_restore(pflags);



	return error;

	if (count)

		return -ENOMEM;

	return 0;

}



/*