[f2fs-dev] [PATCH] f2fs: fix deadlock in f2f2_add_dentry

2023-08-24 Thread Lizhi Xu via Linux-f2fs-devel 
There are two paths:
1. f2fs_add_dentry->f2fs_down_read->f2fs_add_inline_entry->down_write->
   up_write->f2fs_up_read
2. f2fs_add_dentry->f2fs_add_regular_entry->down_write->
   f2fs_init_inode_metadata->f2fs_down_read->f2fs_up_read->up_write

Force order lock to read->write.

Signed-off-by: Lizhi Xu 
Reported-and-tested-by: [email protected]
---
 fs/f2fs/dir.c| 4 +---
 fs/f2fs/inline.c | 2 ++
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c
index d635c58cf5a3..022dc02c1390 100644
--- a/fs/f2fs/dir.c
+++ b/fs/f2fs/dir.c
@@ -736,12 +736,12 @@ int f2fs_add_regular_entry(struct inode *dir, const 
struct f2fs_filename *fname,
f2fs_wait_on_page_writeback(dentry_page, DATA, true, true);
 
if (inode) {
-   f2fs_down_write(&F2FS_I(inode)->i_sem);
page = f2fs_init_inode_metadata(inode, dir, fname, NULL);
if (IS_ERR(page)) {
err = PTR_ERR(page);
goto fail;
}
+   f2fs_down_write(&F2FS_I(inode)->i_sem);
}
 
make_dentry_ptr_block(NULL, &d, dentry_blk);
@@ -780,9 +780,7 @@ int f2fs_add_dentry(struct inode *dir, const struct 
f2fs_filename *fname,
 * Should get i_xattr_sem to keep the lock order:
 * i_xattr_sem -> inode_page lock used by f2fs_setxattr.
 */
-   f2fs_down_read(&F2FS_I(dir)->i_xattr_sem);
err = f2fs_add_inline_entry(dir, fname, inode, ino, mode);
-   f2fs_up_read(&F2FS_I(dir)->i_xattr_sem);
}
if (err == -EAGAIN)
err = f2fs_add_regular_entry(dir, fname, inode, ino, mode);
diff --git a/fs/f2fs/inline.c b/fs/f2fs/inline.c
index 4638fee16a91..7618b383c2b7 100644
--- a/fs/f2fs/inline.c
+++ b/fs/f2fs/inline.c
@@ -628,10 +628,12 @@ int f2fs_add_inline_entry(struct inode *dir, const struct 
f2fs_filename *fname,
if (IS_ERR(ipage))
return PTR_ERR(ipage);
 
+   f2fs_down_read(&F2FS_I(dir)->i_xattr_sem);
inline_dentry = inline_data_addr(dir, ipage);
make_dentry_ptr_inline(dir, &d, inline_dentry);
 
bit_pos = f2fs_room_for_filename(d.bitmap, slots, d.max);
+   f2fs_up_read(&F2FS_I(dir)->i_xattr_sem);
if (bit_pos >= d.max) {
err = do_convert_inline_dir(dir, ipage, inline_dentry);
if (err)
-- 
2.25.1



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Re: [f2fs-dev] [PATCH] f2fs: fix deadlock in f2f2_add_dentry

2023-08-25 Thread Lizhi Xu via Linux-f2fs-devel 
On Fri, 25 Aug 2023 18:41:38, [email protected] wrote:
> Can you please check below patch? it has fixed reported issue.
>
> https://git.kernel.org/pub/scm/linux/kernel/git/jaegeuk/f2fs.git/commit/?h=dev&id=5c13e2388bf3426fd69a89eb46e50469e9624e56
> 
> Feedback from syzbot:
> 
> https://lore.kernel.org/linux-f2fs-devel/[email protected]/
This fix uses nest lock to avoid deadlocks, which I personally believe is 
feasible.


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