ext4: do not let fstrim block system suspend

Len Brown has reported that system suspend sometimes fail due to
inability to freeze a task working in ext4_trim_fs() for one minute.
Trimming a large filesystem on a disk that slowly processes discard
requests can indeed take a long time. Since discard is just an advisory
call, it is perfectly fine to interrupt it at any time and the return
number of discarded blocks until that moment. Do that when we detect the
task is being frozen.

Cc: stable@kernel.org
Reported-by: Len Brown <lenb@kernel.org>
Suggested-by: Dave Chinner <david@fromorbit.com>
References: https://bugzilla.kernel.org/show_bug.cgi?id=216322
Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20230913150504.9054-2-jack@suse.cz
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

Author: jankara

fs/ext4/mballoc.c

@@ -16,6 +16,7 @@
 #include <linux/slab.h>
 #include <linux/nospec.h>
 #include <linux/backing-dev.h>
+#include <linux/freezer.h>
 #include <trace/events/ext4.h>
 
 /*
@@ -6916,6 +6917,11 @@ static ext4_grpblk_t ext4_last_grp_cluster(struct super_block *sb,
 					EXT4_CLUSTER_BITS(sb);
 }
 
+static bool ext4_trim_interrupted(void)
+{
+	return fatal_signal_pending(current) || freezing(current);
+}
+
 static int ext4_try_to_trim_range(struct super_block *sb,
 		struct ext4_buddy *e4b, ext4_grpblk_t start,
 		ext4_grpblk_t max, ext4_grpblk_t minblocks)
@@ -6949,8 +6955,8 @@ __releases(ext4_group_lock_ptr(sb, e4b->bd_group))
 		free_count += next - start;
 		start = next + 1;
 
-		if (fatal_signal_pending(current))
-			return -ERESTARTSYS;
+		if (ext4_trim_interrupted())
+			return count;
 
 		if (need_resched()) {
 			ext4_unlock_group(sb, e4b->bd_group);
@@ -7072,6 +7078,8 @@ int ext4_trim_fs(struct super_block *sb, struct fstrim_range *range)
 	end = EXT4_CLUSTERS_PER_GROUP(sb) - 1;
 
 	for (group = first_group; group <= last_group; group++) {
+		if (ext4_trim_interrupted())
+			break;
 		grp = ext4_get_group_info(sb, group);
 		if (!grp)
 			continue;