On 2019/12/17 22:37, Trond Myklebust wrote:
On Tue, 2019-12-17 at 21:33 +0800, Jia-Ju Bai wrote:
The filesystem may sleep while holding a spinlock.
The function call path (from bottom to top) in Linux 4.19 is:
fs/nfs/pnfs.c, 2052:
pnfs_find_alloc_layout(GFP_KERNEL) in _pnfs_grab_empty_layout
fs/nfs/pnfs.c, 2051:
spin_lock in _pnfs_grab_empty_layout
pnfs_find_alloc_layout(GFP_KERNEL) can sleep at runtime.
To fix this possible bug, GFP_KERNEL is replaced with GFP_ATOMIC for
pnfs_find_alloc_layout().
This bug is found by a static analysis tool STCheck written by
myself.
Signed-off-by: Jia-Ju Bai <baijiaju1990@xxxxxxxxx>
---
fs/nfs/pnfs.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c
index cec3070ab577..cfbe170f0651 100644
--- a/fs/nfs/pnfs.c
+++ b/fs/nfs/pnfs.c
@@ -2138,7 +2138,7 @@ _pnfs_grab_empty_layout(struct inode *ino,
struct nfs_open_context *ctx)
struct pnfs_layout_hdr *lo;
spin_lock(&ino->i_lock);
- lo = pnfs_find_alloc_layout(ino, ctx, GFP_KERNEL);
+ lo = pnfs_find_alloc_layout(ino, ctx, GFP_ATOMIC);
if (!lo)
goto out_unlock;
if (!test_bit(NFS_LAYOUT_INVALID_STID, &lo->plh_flags))
I'm not seeing why this is necessary. As far as I can see,
pnfs_find_alloc_layout() will release the ino->i_lock before sleeping.
False positive?
Thanks for the reply.
You are right, my report is false...
I did not check the definition of pnfs_find_alloc_layout(), sorry...
Best wishes,
Jia-Ju Bai
