linux-kernel - [PATCH 2/2] dm resume: don't return EINVAL when signalled

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Message-ID: <ffe97384-f862-afe0-b83-bcfd2b65b72@redhat.com>
Date: Mon, 5 Aug 2024 17:40:53 +0200 (CEST)
From: Mikulas Patocka <mpatocka@...hat.com>
To: Alasdair Kergon <agk@...hat.com>, Mike Snitzer <snitzer@...nel.org>, 
    dm-devel@...ts.linux.dev, linux-kernel@...r.kernel.org, 
    Khazhismel Kumykov <khazhy@...gle.com>, 
    Zdenek Kabelac <zdenek.kabelac@...il.com>
Subject: [PATCH 2/2] dm resume: don't return EINVAL when signalled

If the dm_resume method is called on a device that is not suspended, the
method will suspend the device briefly, before resuming it (so that the
table will be swapped).

However, there was a bug that the return value of dm_suspended_md was not
checked. dm_suspended_md may return an error when it is interrupted by a
signal. In this case, do_resume would call dm_swap_table, which would
return -EINVAL.

This commit fixes the logic, so that error returned by dm_suspend is
checked and the reusme operation is undone.

Signed-off-by: Mikulas Patocka <mpatocka@...hat.com>
Signed-off-by: Khazhismel Kumykov <khazhy@...gle.com>

---
 drivers/md/dm-ioctl.c |   20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

Index: linux-2.6/drivers/md/dm-ioctl.c
===================================================================
--- linux-2.6.orig/drivers/md/dm-ioctl.c	2024-05-15 16:55:57.000000000 +0200
+++ linux-2.6/drivers/md/dm-ioctl.c	2024-08-05 17:35:32.000000000 +0200
@@ -1181,8 +1181,24 @@ static int do_resume(struct dm_ioctl *pa
 			suspend_flags &= ~DM_SUSPEND_LOCKFS_FLAG;
 		if (param->flags & DM_NOFLUSH_FLAG)
 			suspend_flags |= DM_SUSPEND_NOFLUSH_FLAG;
-		if (!dm_suspended_md(md))
-			dm_suspend(md, suspend_flags);
+		if (!dm_suspended_md(md)) {
+			r = dm_suspend(md, suspend_flags);
+			if (r) {
+				down_write(&_hash_lock);
+				hc = dm_get_mdptr(md);
+				if (hc && !hc->new_map) {
+					hc->new_map = new_map;
+					new_map = NULL;
+				} else {
+					r = -ENXIO;
+				}
+				up_write(&_hash_lock);
+				if (new_map)
+					dm_table_destroy(new_map);
+				dm_put(md);
+				return r;
+			}
+		}
 
 		old_size = dm_get_size(md);
 		old_map = dm_swap_table(md, new_map);