From: Jan Kara <jack@suse.cz>
To: Christian Brauner <brauner@kernel.org>
Cc: <linux-fsdevel@vger.kernel.org>, Hugh Dickins <hughd@google.com>,
<linux-mm@kvack.org>, Mikulas Patocka <mpatocka@redhat.com>,
Jan Kara <jack@suse.cz>
Subject: [PATCH] tmpfs: don't interrupt fallocate with EINTR
Date: Thu, 16 May 2024 00:10:44 +0200 [thread overview]
Message-ID: <20240515221044.590-1-jack@suse.cz> (raw)
From: Mikulas Patocka <mpatocka@redhat.com>
I have a program that sets up a periodic timer with 10ms interval. When
the program attempts to call fallocate(2) on tmpfs, it goes into an
infinite loop. fallocate(2) takes longer than 10ms, so it gets
interrupted by a signal and it returns EINTR. On EINTR, the fallocate
call is restarted, going into the same loop again.
Let's change the signal_pending() check in shmem_fallocate() loop to
fatal_signal_pending(). This solves the problem of shmem_fallocate()
constantly restarting. Since most other filesystem's fallocate methods
don't react to signals, it is unlikely userspace really relies on timely
delivery of non-fatal signals while fallocate is running. Also the
comment before the signal check:
/*
* Good, the fallocate(2) manpage permits EINTR: we may have
* been interrupted because we are using up too much memory.
*/
indicates that the check was mainly added for OOM situations in which
case the process will be sent a fatal signal so this change preserves
the behavior in OOM situations.
[JK: Update changelog and comment based on upstream discussion]
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Jan Kara <jack@suse.cz>
---
mm/shmem.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/mm/shmem.c b/mm/shmem.c
index 1f84a41aeb85..9c148f9723f4 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -3167,10 +3167,13 @@ static long shmem_fallocate(struct file *file, int mode, loff_t offset,
struct folio *folio;
/*
- * Good, the fallocate(2) manpage permits EINTR: we may have
- * been interrupted because we are using up too much memory.
+ * Check for fatal signal so that we abort early in OOM
+ * situations. We don't want to abort in case of non-fatal
+ * signals as large fallocate can take noticeable time and
+ * e.g. periodic timers may result in fallocate constantly
+ * restarting.
*/
- if (signal_pending(current))
+ if (fatal_signal_pending(current))
error = -EINTR;
else if (shmem_falloc.nr_unswapped > shmem_falloc.nr_falloced)
error = -ENOMEM;
--
2.35.3
next reply other threads:[~2024-05-15 22:11 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-15 22:10 Jan Kara [this message]
2024-05-15 23:09 ` [PATCH] tmpfs: don't interrupt fallocate with EINTR Matthew Wilcox
[not found] <ef5c3b-fcd0-db5c-8d4-eeae79e62267@redhat.com>
2024-03-05 8:42 ` Christian Brauner
2024-03-05 9:34 ` Mikulas Patocka
2024-03-05 10:10 ` Christian Brauner
2024-03-05 14:03 ` Mikulas Patocka
2024-03-07 10:47 ` Christian Brauner
2024-03-06 17:49 ` Jan Kara
2024-03-07 10:45 ` Christian Brauner
2024-03-07 14:59 ` Matthew Wilcox
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