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? -- Trond Myklebust Linux NFS client maintainer, Hammerspace trond.myklebust@xxxxxxxxxxxxxxx
