From: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx>
cma_alloc() keep failed in our system which thanks to a jh->bh->b_page
can not be migrated out of CMA area[1] as the jh has one cp_transaction
pending on it because of j_free > j_max_transaction_buffers[2][3][4][5][6].
We temporarily solve this by launching jbd2_log_do_checkpoint forcefully
somewhere. Since journal is common mechanism to all JFSs and
cp_transaction has a little fewer opportunity to be launched, the
cma_alloc() could be affected under the same scenario. This patch
would like to have buffer_head of ext4 not use CMA pages when doing
sb_getblk.
[1]
crash_arm64_v8.0.4++> kmem -p|grep ffffff808f0aa150(sb->s_bdev->bd_inode->i_mapping)
fffffffe01a51c00 e9470000 ffffff808f0aa150 3 2 8000000008020 lru,private
fffffffe03d189c0 174627000 ffffff808f0aa150 4 2 2004000000008020 lru,private
fffffffe03d88e00 176238000 ffffff808f0aa150 3f9 2 2008000000008020 lru,private
fffffffe03d88e40 176239000 ffffff808f0aa150 6 2 2008000000008020 lru,private
fffffffe03d88e80 17623a000 ffffff808f0aa150 5 2 2008000000008020 lru,private
fffffffe03d88ec0 17623b000 ffffff808f0aa150 1 2 2008000000008020 lru,private
fffffffe03d88f00 17623c000 ffffff808f0aa150 0 2 2008000000008020 lru,private
fffffffe040e6540 183995000 ffffff808f0aa150 3f4 2 2004000000008020 lru,private
[2] page -> buffer_head
crash_arm64_v8.0.4++> struct page.private fffffffe01a51c00 -x
private = 0xffffff802fca0c00
[3] buffer_head -> journal_head
crash_arm64_v8.0.4++> struct buffer_head.b_private 0xffffff802fca0c00
b_private = 0xffffff8041338e10,
[4] journal_head -> b_cp_transaction
crash_arm64_v8.0.4++> struct journal_head.b_cp_transaction 0xffffff8041338e10 -x
b_cp_transaction = 0xffffff80410f1900,
[5] transaction_t -> journal
crash_arm64_v8.0.4++> struct transaction_t.t_journal 0xffffff80410f1900 -x
t_journal = 0xffffff80e70f3000,
[6] j_free & j_max_transaction_buffers
crash_arm64_v8.0.4++> struct journal_t.j_free,j_max_transaction_buffers 0xffffff80e70f3000 -x
j_free = 0x3f1,
j_max_transaction_buffers = 0x100,
Suggested-by: Theodore Ts'o <tytso@xxxxxxx>
Signed-off-by: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx>
---
v2: switch to use getblk_unmoveable as suggested by Theodore Ts'o
---
---
fs/ext4/inode.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 941c1c0d5c6e..a0f48840c5c1 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -869,7 +869,14 @@ struct buffer_head *ext4_getblk(handle_t *handle, struct inode *inode,
if (nowait)
return sb_find_get_block(inode->i_sb, map.m_pblk);
- bh = sb_getblk(inode->i_sb, map.m_pblk);
+ /*
+ * Since bh could introduce extra ref count such as referred by
+ * journal_head etc. Try to avoid using __GFP_MOVABLE here
+ * as it may fail the migration when journal_head remains.
+ */
+ bh = getblk_unmovable(inode->i_sb->s_bdev, map.m_pblk,
+ inode->i_sb->s_blocksize);
+
if (unlikely(!bh))
return ERR_PTR(-ENOMEM);
if (map.m_flags & EXT4_MAP_NEW) {
--
2.25.1
