Commit 74e797d7 authored by David Howells's avatar David Howells
Browse files

mm: Provide a means of invalidation without using launder_folio 



Implement a replacement for launder_folio.  The key feature of
invalidate_inode_pages2() is that it locks each folio individually, unmaps
it to prevent mmap'd accesses interfering and calls the ->launder_folio()
address_space op to flush it.  This has problems: firstly, each folio is
written individually as one or more small writes; secondly, adjacent folios
cannot be added so easily into the laundry; thirdly, it's yet another op to
implement.

Instead, use the invalidate lock to cause anyone wanting to add a folio to
the inode to wait, then unmap all the folios if we have mmaps, then,
conditionally, use ->writepages() to flush any dirty data back and then
discard all pages.

The invalidate lock prevents ->read_iter(), ->write_iter() and faulting
through mmap all from adding pages for the duration.

This is then used from netfslib to handle the flusing in unbuffered and
direct writes.

Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
cc: Matthew Wilcox <willy@infradead.org>
cc: Miklos Szeredi <miklos@szeredi.hu>
cc: Trond Myklebust <trond.myklebust@hammerspace.com>
cc: Christoph Hellwig <hch@lst.de>
cc: Andrew Morton <akpm@linux-foundation.org>
cc: Alexander Viro <viro@zeniv.linux.org.uk>
cc: Christian Brauner <brauner@kernel.org>
cc: Jeff Layton <jlayton@kernel.org>
cc: linux-mm@kvack.org
cc: linux-fsdevel@vger.kernel.org
cc: netfs@lists.linux.dev
cc: v9fs@lists.linux.dev
cc: linux-afs@lists.infradead.org
cc: ceph-devel@vger.kernel.org
cc: linux-cifs@vger.kernel.org
cc: linux-nfs@vger.kernel.org
cc: devel@lists.orangefs.org
parent 120b8781

fs/netfs/direct_write.c

+24 −4
Original line number Diff line number Diff line
@@ -132,12 +132,14 @@ static ssize_t netfs_unbuffered_write_iter_locked(struct kiocb *iocb, struct iov 
ssize_t netfs_unbuffered_write_iter(struct kiocb *iocb, struct iov_iter *from)

{

	struct file *file = iocb->ki_filp;

	struct inode *inode = file->f_mapping->host;

	struct address_space *mapping = file->f_mapping;

	struct inode *inode = mapping->host;

	struct netfs_inode *ictx = netfs_inode(inode);

	unsigned long long end;

	ssize_t ret;

	loff_t pos = iocb->ki_pos;

	unsigned long long end = pos + iov_iter_count(from) - 1;



	_enter("%llx,%zx,%llx", iocb->ki_pos, iov_iter_count(from), i_size_read(inode));

	_enter("%llx,%zx,%llx", pos, iov_iter_count(from), i_size_read(inode));



	if (!iov_iter_count(from))

		return 0;
@@ -157,7 +159,25 @@ ssize_t netfs_unbuffered_write_iter(struct kiocb *iocb, struct iov_iter *from) 
	ret = file_update_time(file);

	if (ret < 0)

		goto out;

	ret = kiocb_invalidate_pages(iocb, iov_iter_count(from));

	if (iocb->ki_flags & IOCB_NOWAIT) {

		/* We could block if there are any pages in the range. */

		ret = -EAGAIN;

		if (filemap_range_has_page(mapping, pos, end))

			if (filemap_invalidate_inode(inode, true, pos, end))

				goto out;

	} else {

		ret = filemap_write_and_wait_range(mapping, pos, end);

		if (ret < 0)

			goto out;

	}



	/*

	 * After a write we want buffered reads to be sure to go to disk to get

	 * the new data.  We invalidate clean cached page from the region we're

	 * about to write.  We do this *before* the write so that we can return

	 * without clobbering -EIOCBQUEUED from ->direct_IO().

	 */

	ret = filemap_invalidate_inode(inode, true, pos, end);

	if (ret < 0)

		goto out;

	end = iocb->ki_pos + iov_iter_count(from);

include/linux/pagemap.h

+2 −0
Original line number Diff line number Diff line
@@ -40,6 +40,8 @@ int filemap_fdatawait_keep_errors(struct address_space *mapping); 
int filemap_fdatawait_range(struct address_space *, loff_t lstart, loff_t lend);

int filemap_fdatawait_range_keep_errors(struct address_space *mapping,

		loff_t start_byte, loff_t end_byte);

int filemap_invalidate_inode(struct inode *inode, bool flush,

			     loff_t start, loff_t end);



static inline int filemap_fdatawait(struct address_space *mapping)

{

mm/filemap.c

+54 −0
Original line number Diff line number Diff line
@@ -4134,6 +4134,60 @@ bool filemap_release_folio(struct folio *folio, gfp_t gfp) 
}

EXPORT_SYMBOL(filemap_release_folio);



/**

 * filemap_invalidate_inode - Invalidate/forcibly write back a range of an inode's pagecache

 * @inode: The inode to flush

 * @flush: Set to write back rather than simply invalidate.

 * @start: First byte to in range.

 * @end: Last byte in range (inclusive), or LLONG_MAX for everything from start

 *       onwards.

 *

 * Invalidate all the folios on an inode that contribute to the specified

 * range, possibly writing them back first.  Whilst the operation is

 * undertaken, the invalidate lock is held to prevent new folios from being

 * installed.

 */

int filemap_invalidate_inode(struct inode *inode, bool flush,

			     loff_t start, loff_t end)

{

	struct address_space *mapping = inode->i_mapping;

	pgoff_t first = start >> PAGE_SHIFT;

	pgoff_t last = end >> PAGE_SHIFT;

	pgoff_t nr = end == LLONG_MAX ? ULONG_MAX : last - first + 1;



	if (!mapping || !mapping->nrpages || end < start)

		goto out;



	/* Prevent new folios from being added to the inode. */

	filemap_invalidate_lock(mapping);



	if (!mapping->nrpages)

		goto unlock;



	unmap_mapping_pages(mapping, first, nr, false);



	/* Write back the data if we're asked to. */

	if (flush) {

		struct writeback_control wbc = {

			.sync_mode	= WB_SYNC_ALL,

			.nr_to_write	= LONG_MAX,

			.range_start	= start,

			.range_end	= end,

		};



		filemap_fdatawrite_wbc(mapping, &wbc);

	}



	/* Wait for writeback to complete on all folios and discard. */

	truncate_inode_pages_range(mapping, start, end);



unlock:

	filemap_invalidate_unlock(mapping);

out:

	return filemap_check_errors(mapping);

}

EXPORT_SYMBOL_GPL(filemap_invalidate_inode);



#ifdef CONFIG_CACHESTAT_SYSCALL

/**

 * filemap_cachestat() - compute the page cache statistics of a mapping