+ mpage-terminate-read-ahead-on-read-error.patch added to mm-new branch

+ mpage-terminate-read-ahead-on-read-error.patch added to mm-new branch

[Andrew Morton]

The patch titled
     Subject: mpage: terminate read-ahead on read error
has been added to the -mm mm-new branch.  Its filename is
     mpage-terminate-read-ahead-on-read-error.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mpage-terminate-read-ahead-on-read-error.patch

This patch will later appear in the mm-new branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
notice and to finish up reviews.  Please do not hesitate to respond to
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fixup patches in mm-new.

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------------------------------------------------------
From: Chi Zhiling <chizhiling@kylinos.cn>
Subject: mpage: terminate read-ahead on read error
Date: Tue, 12 Aug 2025 15:22:23 +0800

For exFAT filesystems with 4MB read_ahead_size, removing the storage
device during read operations can delay EIO error reporting by several
minutes.  This occurs because the read-ahead implementation in mpage
doesn't handle errors.

Another reason for the delay is that the filesystem requires metadata to
issue file read request.  When the storage device is removed, the metadata
buffers are invalidated, causing mpage to repeatedly attempt to fetch
metadata during each get_block call.

The original purpose of this patch is terminate read ahead when we fail to
get metadata, to make the patch more generic, implement it by checking
folio status, instead of checking the return of get_block().

Link: https://lkml.kernel.org/r/20250812072225.181798-1-chizhiling@163.com
Signed-off-by: Chi Zhiling <chizhiling@kylinos.cn>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Namjae Jeon <linkinjeon@kernel.org>
Cc: Sungjong Seo <sj1557.seo@samsung.com>
Cc: Yuezhang Mo <Yuezhang.Mo@sony.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 fs/mpage.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/fs/mpage.c~mpage-terminate-read-ahead-on-read-error
+++ a/fs/mpage.c
@@ -369,6 +369,9 @@ void mpage_readahead(struct readahead_co
 		args.folio = folio;
 		args.nr_pages = readahead_count(rac);
 		args.bio = do_mpage_readpage(&args);
+		if (!folio_test_locked(folio) &&
+		    !folio_test_uptodate(folio))
+			break;
 	}
 	if (args.bio)
 		mpage_bio_submit_read(args.bio);
_

Patches currently in -mm which might be from chizhiling@kylinos.cn are

mm-filemap-do-not-use-is_partially_uptodate-for-entire-folio.patch
mm-filemap-skip-non-uptodate-folio-if-there-are-available-folios.patch
mpage-terminate-read-ahead-on-read-error.patch
mpage-clean-up-do_mpage_readpage.patch
mpage-convert-do_mpage_readpage-to-return-int-type.patch