From: Naoto Kobayashi <naoto.kobayashi4c@gmail.com>
To: tytso@mit.edu, adilger.kernel@dilger.ca
Cc: Naoto Kobayashi <naoto.kobayashi4c@gmail.com>,
linux-ext4@vger.kernel.org
Subject: [PATCH v2 3/3] ext4: Prevent ext4_kvmalloc_nofs() from re-entering the filesystem and deadlocking
Date: Fri, 27 Dec 2019 17:05:23 +0900 [thread overview]
Message-ID: <20191227080523.31808-4-naoto.kobayashi4c@gmail.com> (raw)
In-Reply-To: <20191227080523.31808-1-naoto.kobayashi4c@gmail.com>
Even if __vmalloc() receives GFP_NOFS, this function allocates
data pages and auxiliary structures (e.g. pagetables) with __GFP_FS[1].
To prevent memory reclaim from re-entering the filesystem here and
potentially deadlocking, use memalloc_nofs_save() that gets
__vmalloc() to drop __GFP_FS.
[1] linux-tree/Documentation/core-api/gfp-mask-fs-io.rst
Signed-off-by: Naoto Kobayashi <naoto.kobayashi4c@gmail.com>
---
fs/ext4/super.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index e8965aa6ecce..7f4c9a43a3f3 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -43,6 +43,7 @@
#include <linux/uaccess.h>
#include <linux/iversion.h>
#include <linux/unicode.h>
+#include <linux/sched/mm.h>
#include <linux/kthread.h>
#include <linux/freezer.h>
@@ -206,11 +207,13 @@ void ext4_superblock_csum_set(struct super_block *sb)
void *ext4_kvmalloc_nofs(size_t size)
{
+ unsigned int nofs_flag;
void *ret;
- ret = kmalloc(size, GFP_NOFS | __GFP_NOWARN);
- if (!ret)
- ret = __vmalloc(size, GFP_NOFS, PAGE_KERNEL);
+ /* kvmalloc() does not support GFP_NOFS */
+ nofs_flag = memalloc_nofs_save();
+ ret = kvmalloc(size, GFP_KERNEL);
+ memalloc_nofs_restore(nofs_flag);
return ret;
}
--
2.16.6
prev parent reply other threads:[~2019-12-27 8:05 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-27 8:05 [PATCH v2 0/3] ext4: Prevent memory reclaim from re-entering the filesystem and deadlocking Naoto Kobayashi
2019-12-27 8:05 ` [PATCH v2 1/3] ext4: Delete ext4_kvzvalloc() Naoto Kobayashi
2020-01-09 9:51 ` Jan Kara
2020-01-13 22:32 ` Theodore Y. Ts'o
2019-12-27 8:05 ` [PATCH v2 2/3] ext4: Rename ext4_kvmalloc() to ext4_kvmalloc_nofs() and drop its flags argument Naoto Kobayashi
2020-01-09 10:00 ` Jan Kara
2020-01-13 22:32 ` Theodore Y. Ts'o
2020-01-16 12:37 ` Jan Kara
2020-01-16 15:12 ` Theodore Y. Ts'o
2020-01-16 15:50 ` [PATCH] ext4: drop ext4_kvmalloc() Theodore Ts'o
2020-01-17 10:30 ` Jan Kara
2020-01-17 16:36 ` Theodore Y. Ts'o
2019-12-27 8:05 ` Naoto Kobayashi [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20191227080523.31808-4-naoto.kobayashi4c@gmail.com \
--to=naoto.kobayashi4c@gmail.com \
--cc=adilger.kernel@dilger.ca \
--cc=linux-ext4@vger.kernel.org \
--cc=tytso@mit.edu \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).