[PATCH AUTOSEL 5.7 315/388] ceph: don't return -ESTALE if there's still an open file

Sasha Levin
2020-06-18T01:17:30Z

From: Luis Henriques <lhenriques@suse.com>

[ Upstream commit 878dabb64117406abd40977b87544d05bb3031fc ]

Similarly to commit 03f219041fdb ("ceph: check i_nlink while converting
a file handle to dentry"), this fixes another corner case with
name_to_handle_at/open_by_handle_at. The issue has been detected by
xfstest generic/467, when doing:

- name_to_handle_at("/cephfs/myfile")
- open("/cephfs/myfile")
- unlink("/cephfs/myfile")
- sync; sync;
- drop caches
- open_by_handle_at()

The call to open_by_handle_at should not fail because the file hasn't been
deleted yet (only unlinked) and we do have a valid handle to it. -ESTALE
shall be returned only if i_nlink is 0 *and* i_count is 1.

This patch also makes sure we have LINK caps before checking i_nlink.

Signed-off-by: Luis Henriques <lhenriques@suse.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Acked-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/ceph/export.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/fs/ceph/export.c b/fs/ceph/export.c
index 79dc06881e78..e088843a7734 100644
--- a/fs/ceph/export.c
+++ b/fs/ceph/export.c
@@ -172,9 +172,16 @@ struct inode *ceph_lookup_inode(struct super_block *sb, u64 ino)
static struct dentry *__fh_to_dentry(struct super_block *sb, u64 ino)
{
struct inode *inode = __lookup_inode(sb, ino);
+ int err;
+
if (IS_ERR(inode))
return ERR_CAST(inode);
- if (inode->i_nlink == 0) {
+ /* We need LINK caps to reliably check i_nlink */
+ err = ceph_do_getattr(inode, CEPH_CAP_LINK_SHARED, false);
+ if (err)
+ return ERR_PTR(err);
+ /* -ESTALE if inode as been unlinked and no file is open */
+ if ((inode->i_nlink == 0) && (atomic_read(&inode->i_count) == 1)) {
iput(inode);
return ERR_PTR(-ESTALE);
}
--
2.25.1