[PATCH 5.4 017/344] f2fs: call f2fs_balance_fs outside of locked page

Greg Kroah-Hartman
2020-02-21T08:01:47Z

From: Jaegeuk Kim <jaegeuk@kernel.org>

[ Upstream commit bdf03299248916640a835a05d32841bb3d31912d ]

Otherwise, we can hit deadlock by waiting for the locked page in
move_data_block in GC.

Thread A Thread B
- do_page_mkwrite
- f2fs_vm_page_mkwrite
- lock_page
- f2fs_balance_fs
- mutex_lock(gc_mutex)
- f2fs_gc
- do_garbage_collect
- ra_data_block
- grab_cache_page
- f2fs_balance_fs
- mutex_lock(gc_mutex)

Fixes: 39a8695824510 ("f2fs: refactor ->page_mkwrite() flow")
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/f2fs/file.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 44bc5f4a9ce19..c3a9da79ac997 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -50,7 +50,7 @@ static vm_fault_t f2fs_vm_page_mkwrite(struct vm_fault *vmf)
struct page *page = vmf->page;
struct inode *inode = file_inode(vmf->vma->vm_file);
struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
- struct dnode_of_data dn = { .node_changed = false };
+ struct dnode_of_data dn;
int err;

if (unlikely(f2fs_cp_error(sbi))) {
@@ -63,6 +63,9 @@ static vm_fault_t f2fs_vm_page_mkwrite(struct vm_fault *vmf)
goto err;
}

+ /* should do out of any locked page */
+ f2fs_balance_fs(sbi, true);
+
sb_start_pagefault(inode->i_sb);

f2fs_bug_on(sbi, f2fs_has_inline_data(inode));
@@ -120,8 +123,6 @@ static vm_fault_t f2fs_vm_page_mkwrite(struct vm_fault *vmf)
out_sem:
up_read(&F2FS_I(inode)->i_mmap_sem);

- f2fs_balance_fs(sbi, dn.node_changed);
-
sb_end_pagefault(inode->i_sb);
err:
return block_page_mkwrite_return(err);
--
2.20.1