NFS: Fix potential oops in nfs_inode_remove_request()

Once a folio's private data has been cleared, it's possible for another
process to clear the folio->mapping (e.g. via invalidate_complete_folio2
or evict_mapping_folio), so it wouldn't be safe to call
nfs_page_to_inode() after that.

Fixes: 0c493b5cf16e ("NFS: Convert buffered writes to use folios")
Signed-off-by: Scott Mayhew <smayhew@redhat.com>
Reviewed-by: Benjamin Coddington <bcodding@redhat.com>
Tested-by: Benjamin Coddington <bcodding@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index 7720b5e..9d82d50 100644 (file)
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -788,6 +788,8 @@ static void nfs_inode_add_request(struct nfs_page *req)
  */
 static void nfs_inode_remove_request(struct nfs_page *req)
 {
+       struct nfs_inode *nfsi = NFS_I(nfs_page_to_inode(req));
+
        if (nfs_page_group_sync_on_bit(req, PG_REMOVE)) {
                struct folio *folio = nfs_page_to_folio(req->wb_head);
                struct address_space *mapping = folio_file_mapping(folio);
@@ -802,7 +804,7 @@ static void nfs_inode_remove_request(struct nfs_page *req)
        }
 
        if (test_and_clear_bit(PG_INODE_REF, &req->wb_flags)) {
-               atomic_long_dec(&NFS_I(nfs_page_to_inode(req))->nrequests);
+               atomic_long_dec(&nfsi->nrequests);
                nfs_release_request(req);
        }
 }