direct reclaim doesn't write out filesystem page, only kswapd could do
it. So, if the call comes from direct reclaim, it is definitely a bug.
And, Mel Gormane also mentioned "Ultimately, this will be a BUG_ON." In
commit 94054fa3fca1fd78db02cb3d68d5627120f0a1d4 ("xfs: warn if direct
reclaim tries to writeback pages").
Although it is for xfs, ext4 has the similar behavior, so elevate
WARN_ON to BUG_ON.
And, correct the comment accordingly.
Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: "Theodore Ts'o" <tytso@xxxxxxx>
Cc: Andreas Dilger <adilger.kernel@xxxxxxxxx>
Signed-off-by: Yang Shi <yang.shi@xxxxxxxxxxxxxxxxx>
---
fs/ext4/inode.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 2ea07ef..089e388 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -2071,7 +2071,7 @@ static int __ext4_journalled_writepage(struct page *page,
* This function can get called via...
* - ext4_writepages after taking page lock (have journal handle)
* - journal_submit_inode_data_buffers (no journal handle)
- * - shrink_page_list via the kswapd/direct reclaim (no journal handle)
+ * - shrink_page_list via the kswapd (no journal handle)
* - grab_page_cache when doing write_begin (have journal handle)
*
* We don't do any block allocation in this function. If we have page with
@@ -2148,10 +2148,10 @@ static int ext4_writepage(struct page *page,
(inode->i_sb->s_blocksize == PAGE_SIZE)) {
/*
* For memory cleaning there's no point in writing only
- * some buffers. So just bail out. Warn if we came here
- * from direct reclaim.
+ * some buffers. So just bail out. It is a bug if we
+ * came here from direct reclaim.
*/
- WARN_ON_ONCE((current->flags & (PF_MEMALLOC|PF_KSWAPD))
+ BUG_ON((current->flags & (PF_MEMALLOC|PF_KSWAPD))
== PF_MEMALLOC);
unlock_page(page);
return 0;
--
1.8.3.1
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