linux-kernel - [PATCH] cachefiles: Drop superfluous readpages aops NULL check

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Message-ID: <161115907229.1175773.15191598530409204569.stgit@warthog.procyon.org.uk>
Date:   Wed, 20 Jan 2021 16:11:12 +0000
From:   David Howells <dhowells@...hat.com>
To:     torvalds@...ux-foundation.org
Cc:     Takashi Iwai <tiwai@...e.de>,
        "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        dhowells@...hat.com, linux-afs@...ts.infradead.org,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] cachefiles: Drop superfluous readpages aops NULL check

From: Takashi Iwai <tiwai@...e.de>

After the recent actions to convert readpages aops to readahead, the
NULL checks of readpages aops in cachefiles_read_or_alloc_page() may
hit falsely.  More badly, it's an ASSERT() call, and this panics.

Drop the superfluous NULL checks for fixing this regression.

[DH: Note that cachefiles never actually used readpages, so this check was
 never actually necessary]

BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=208883
BugLink: https://bugzilla.opensuse.org/show_bug.cgi?id=1175245
Fixes: 9ae326a69004 ("CacheFiles: A cache that backs onto a mounted filesystem")
Signed-off-by: Takashi Iwai <tiwai@...e.de>
Signed-off-by: David Howells <dhowells@...hat.com>
Acked-by: Matthew Wilcox (Oracle) <willy@...radead.org>
---

 fs/cachefiles/rdwr.c |    2 --
 1 file changed, 2 deletions(-)

diff --git a/fs/cachefiles/rdwr.c b/fs/cachefiles/rdwr.c
index 8bda092e60c5..e027c718ca01 100644
--- a/fs/cachefiles/rdwr.c
+++ b/fs/cachefiles/rdwr.c
@@ -413,7 +413,6 @@ int cachefiles_read_or_alloc_page(struct fscache_retrieval *op,
 
 	inode = d_backing_inode(object->backer);
 	ASSERT(S_ISREG(inode->i_mode));
-	ASSERT(inode->i_mapping->a_ops->readpages);
 
 	/* calculate the shift required to use bmap */
 	shift = PAGE_SHIFT - inode->i_sb->s_blocksize_bits;
@@ -713,7 +712,6 @@ int cachefiles_read_or_alloc_pages(struct fscache_retrieval *op,
 
 	inode = d_backing_inode(object->backer);
 	ASSERT(S_ISREG(inode->i_mode));
-	ASSERT(inode->i_mapping->a_ops->readpages);
 
 	/* calculate the shift required to use bmap */
 	shift = PAGE_SHIFT - inode->i_sb->s_blocksize_bits;