ext4: re-enable -o discard functionality in no-journal mode

This is a revert of commit b56ff9d397ce, which removed the call to
ext4_issue_discard() to fix a BUG reported because
ext4_issue_discard() was being called from inside a block group
spinlock.  As it turns out this bug had already been fixed by Lukas
Czerner in commit 53fdcf992d61 by the simple expedient of moving when
we call ext4_issue_discard() outside the spinlock.

So it should be safe to re-enable this functionality, which I tested
by putting an BUG_ON(in_atomic) just after the restored callsite to
ext4_issue_discard().

Addresses-Google-Bug: #6750518

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: Anatol Pomozov <anatol.pomozov@gmail.com>

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 2102c20f7e989bee11d3bb5e662b836e9ab8730d..2c7c082b8169e78d903f3c9ac6640c6442d3544a 100644 (file)
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -4656,6 +4656,8 @@ do_more:
                 * with group lock held. generate_buddy look at
                 * them with group lock_held
                 */
+               if (test_opt(sb, DISCARD))
+                       ext4_issue_discard(sb, block_group, bit, count);
                ext4_lock_group(sb, block_group);
                mb_clear_bits(bitmap_bh->b_data, bit, count_clusters);
                mb_free_blocks(inode, &e4b, bit, count_clusters);