[PATCH v3 3/3] btrfs: Don't block system suspend during fstrim

[Luca Stefani <luca.stefani.ge1@gmail.com>]

Sometimes the system isn't able to suspend because the task
responsible for trimming the device isn't able to finish in
time, especially since we have a free extent discarding phase,
which can trim a lot of unallocated space, and there is no
limits on the trim size (unlike the block group part).

Since discard isn't a critical call it can be interrupted
at any time, in such cases we stop the trim, report the amount
of discarded bytes and return failure.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=219180
Link: https://bugzilla.suse.com/show_bug.cgi?id=1229737
Signed-off-by: Luca Stefani <luca.stefani.ge1@gmail.com>
---
 fs/btrfs/extent-tree.c | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 9c1ddf13659e..ee4daaa56b95 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -16,6 +16,7 @@
 #include <linux/percpu_counter.h>
 #include <linux/lockdep.h>
 #include <linux/crc32c.h>
+#include <linux/freezer.h>
 #include "ctree.h"
 #include "extent-tree.h"
 #include "transaction.h"
@@ -1235,6 +1236,11 @@ static int remove_extent_backref(struct btrfs_trans_handle *trans,
 	return ret;
 }
 
+static bool btrfs_trim_interrupted(void)
+{
+	return fatal_signal_pending(current) || freezing(current);
+}
+
 static int btrfs_issue_discard(struct block_device *bdev, u64 start, u64 len,
 			       u64 *discarded_bytes)
 {
@@ -1318,6 +1324,11 @@ static int btrfs_issue_discard(struct block_device *bdev, u64 start, u64 len,
 
 			start += bytes_to_discard;
 			bytes_left -= bytes_to_discard;
+
+			if (btrfs_trim_interrupted()) {
+				ret = -ERESTARTSYS;
+				break;
+			}
 		}
 	}
 
@@ -6473,7 +6484,7 @@ static int btrfs_trim_free_extents(struct btrfs_device *device, u64 *trimmed)
 		start += len;
 		*trimmed += bytes;
 
-		if (fatal_signal_pending(current)) {
+		if (btrfs_trim_interrupted()) {
 			ret = -ERESTARTSYS;
 			break;
 		}
@@ -6522,6 +6533,9 @@ int btrfs_trim_fs(struct btrfs_fs_info *fs_info, struct fstrim_range *range)
 
 	cache = btrfs_lookup_first_block_group(fs_info, range->start);
 	for (; cache; cache = btrfs_next_block_group(cache)) {
+		if (btrfs_trim_interrupted())
+			break;
+
 		if (cache->start >= range_end) {
 			btrfs_put_block_group(cache);
 			break;
@@ -6561,6 +6575,9 @@ int btrfs_trim_fs(struct btrfs_fs_info *fs_info, struct fstrim_range *range)
 
 	mutex_lock(&fs_devices->device_list_mutex);
 	list_for_each_entry(device, &fs_devices->devices, dev_list) {
+		if (btrfs_trim_interrupted())
+			break;
+
 		if (test_bit(BTRFS_DEV_STATE_MISSING, &device->dev_state))
 			continue;
 
-- 
2.46.0