linux-kernel - [PATCH v21 01/30] splice: Fix filemap of a blockdev

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Date:   Sat, 20 May 2023 01:00:20 +0100
From:   David Howells <dhowells@...hat.com>
To:     Jens Axboe <axboe@...nel.dk>, Al Viro <viro@...iv.linux.org.uk>,
        Christoph Hellwig <hch@...radead.org>
Cc:     David Howells <dhowells@...hat.com>,
        Matthew Wilcox <willy@...radead.org>, Jan Kara <jack@...e.cz>,
        Jeff Layton <jlayton@...nel.org>,
        David Hildenbrand <david@...hat.com>,
        Jason Gunthorpe <jgg@...dia.com>,
        Logan Gunthorpe <logang@...tatee.com>,
        Hillf Danton <hdanton@...a.com>,
        Christian Brauner <brauner@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-fsdevel@...r.kernel.org, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Christoph Hellwig <hch@....de>,
        Steve French <stfrench@...rosoft.com>,
        John Hubbard <jhubbard@...dia.com>
Subject: [PATCH v21 01/30] splice: Fix filemap of a blockdev

Fix filemap_splice_read() to use file->f_mapping->host, not file->f_inode,
as the source of the file size because in the case of a block device,
file->f_inode points to the block-special file (which is typically 0
length) and not the backing store.

Fixes: 07073eb01c5f ("splice: Add a func to do a splice from a buffered file without ITER_PIPE")
Signed-off-by: David Howells <dhowells@...hat.com>
Reviewed-by: Christoph Hellwig <hch@....de>
cc: Steve French <stfrench@...rosoft.com>
cc: Jens Axboe <axboe@...nel.dk>
cc: Al Viro <viro@...iv.linux.org.uk>
cc: David Hildenbrand <david@...hat.com>
cc: John Hubbard <jhubbard@...dia.com>
cc: linux-mm@...ck.org
cc: linux-block@...r.kernel.org
cc: linux-fsdevel@...r.kernel.org
---
 mm/filemap.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/filemap.c b/mm/filemap.c
index b4c9bd368b7e..a2006936a6ae 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2900,7 +2900,7 @@ ssize_t filemap_splice_read(struct file *in, loff_t *ppos,
 	do {
 		cond_resched();
 
-		if (*ppos >= i_size_read(file_inode(in)))
+		if (*ppos >= i_size_read(in->f_mapping->host))
 			break;
 
 		iocb.ki_pos = *ppos;
@@ -2916,7 +2916,7 @@ ssize_t filemap_splice_read(struct file *in, loff_t *ppos,
 		 * part of the page is not copied back to userspace (unless
 		 * another truncate extends the file - this is desired though).
 		 */
-		isize = i_size_read(file_inode(in));
+		isize = i_size_read(in->f_mapping->host);
 		if (unlikely(*ppos >= isize))
 			break;
 		end_offset = min_t(loff_t, isize, *ppos + len);