linux-kernel - [PATCH] splice: Fix filemap of a blockdev

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Date:   Wed, 19 Apr 2023 09:54:11 +0100
From:   David Howells <dhowells@...hat.com>
To:     Jens Axboe <axboe@...nel.dk>
cc:     dhowells@...hat.com, Ayush Jain <ayush.jain3@....com>,
        Christoph Hellwig <hch@....de>,
        Al Viro <viro@...iv.linux.org.uk>,
        David Hildenbrand <david@...hat.com>,
        John Hubbard <jhubbard@...dia.com>,
        Steve French <stfrench@...rosoft.com>, linux-mm@...ck.org,
        linux-block@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] splice: Fix filemap of a blockdev

Fix the new filemap_splice_read() function to get i_size from
in->f_mapping->host, not in->f_inode so that it works with block devices
too (in->f_inode points to the device file, which is typically zero size).

Fixes: 07073eb01c5f ("splice: Add a func to do a splice from a buffered file without ITER_PIPE")
Link: https://lore.kernel.org/r/0c6b661c-f7ff-cf12-b7f0-00b6b2f1317b@amd.com/
Reported-by: Ayush Jain <ayush.jain3@....com>
cc: Jens Axboe <axboe@...nel.dk>
cc: Christoph Hellwig <hch@....de>
cc: Al Viro <viro@...iv.linux.org.uk>
cc: David Hildenbrand <david@...hat.com>
cc: John Hubbard <jhubbard@...dia.com>
cc: Steve French <stfrench@...rosoft.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 470be06b6096..f86cc8acf33a 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2902,7 +2902,7 @@ 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;
@@ -2918,7 +2918,7 @@ 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);