[PATCH] f2fs: protect new segment allocation in expand_inode_data

From: Daeho Jeong
Date: Sun May 31 2020 - 23:03:56 EST

From: Daeho Jeong <daehojeong@xxxxxxxxxx>

Found a new segemnt allocation without f2fs_lock_op() in
expand_inode_data(). So, when we do fallocate() for a pinned file
and trigger checkpoint very frequently and simultaneously. F2FS gets
stuck in the below code of do_checkpoint() forever.

f2fs_sync_meta_pages(sbi, META, LONG_MAX, FS_CP_META_IO);
/* Wait for all dirty meta pages to be submitted for IO */
<= if fallocate() here,
f2fs_wait_on_all_pages(sbi, F2FS_DIRTY_META); <= it'll wait forever.

Signed-off-by: Daeho Jeong <daehojeong@xxxxxxxxxx>
Reviewed-by: Chao Yu <yuchao0@xxxxxxxxxx>
fs/f2fs/file.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index f7de2a1da528..14ace885baa9 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -1660,7 +1660,11 @@ static int expand_inode_data(struct inode *inode, loff_t offset,

map.m_seg_type = CURSEG_COLD_DATA_PINNED;
+ f2fs_lock_op(sbi);
f2fs_allocate_new_segments(sbi, CURSEG_COLD_DATA);
+ f2fs_unlock_op(sbi);
err = f2fs_map_blocks(inode, &map, 1, F2FS_GET_BLOCK_PRE_DIO);