Date:   Tue, 23 Apr 2019 14:13:29 -0700
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Subject: [PATCH v2] ext4: cond_resched in work-heavy group loops
From:   Khazhismel Kumykov <khazhy@google.com>
To:     tytso@mit.edu, adilger.kernel@dilger.ca
Cc:     linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org,
        jack@suse.cz, Khazhismel Kumykov <khazhy@google.com>
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Sender: linux-ext4-owner@vger.kernel.org
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These functions may take a long time looping over many groups, which
may cause issues for non-preempt kernels.
ext4_mb_init_backend()
ext4_setup_system_zone()
ext4_mb_release()

Signed-off-by: Khazhismel Kumykov <khazhy@google.com>
---
v2: 
 - a few other places that in testing showed to be slow

 fs/ext4/block_validity.c | 1 +
 fs/ext4/mballoc.c        | 2 ++
 2 files changed, 3 insertions(+)

diff --git a/fs/ext4/block_validity.c b/fs/ext4/block_validity.c
index 913061c0de1b..16134469ea3c 100644
--- a/fs/ext4/block_validity.c
+++ b/fs/ext4/block_validity.c
@@ -155,6 +155,7 @@ int ext4_setup_system_zone(struct super_block *sb)
 		return 0;
 
 	for (i=0; i < ngroups; i++) {
+		cond_resched();
 		if (ext4_bg_has_super(sb, i) &&
 		    ((i < 5) || ((i % flex_size) == 0)))
 			add_system_zone(sbi, ext4_group_first_block_no(sb, i),
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 8ef5f12bbee2..99ba720dbb7a 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -2490,6 +2490,7 @@ static int ext4_mb_init_backend(struct super_block *sb)
 	sbi->s_buddy_cache->i_ino = EXT4_BAD_INO;
 	EXT4_I(sbi->s_buddy_cache)->i_disksize = 0;
 	for (i = 0; i < ngroups; i++) {
+		cond_resched();
 		desc = ext4_get_group_desc(sb, i, NULL);
 		if (desc == NULL) {
 			ext4_msg(sb, KERN_ERR, "can't read descriptor %u", i);
@@ -2705,6 +2706,7 @@ int ext4_mb_release(struct super_block *sb)
 
 	if (sbi->s_group_info) {
 		for (i = 0; i < ngroups; i++) {
+			cond_resched();
 			grinfo = ext4_get_group_info(sb, i);
 #ifdef DOUBLE_CHECK
 			kfree(grinfo->bb_bitmap);
-- 
2.21.0.593.g511ec345e18-goog