[PATCH 1/1] NFS: Fix potential oops in nfs_inode_remove_request()

[Scott Mayhew <smayhew@redhat.com>]

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>
---
 fs/nfs/write.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index f4cca8f00c0c..489c3f9dae23 100644
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -785,6 +785,8 @@ 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);
@@ -800,7 +802,7 @@ static void nfs_inode_remove_request(struct nfs_page *req)
 
 	if (test_and_clear_bit(PG_INODE_REF, &req->wb_flags)) {
 		nfs_release_request(req);
-		atomic_long_dec(&NFS_I(nfs_page_to_inode(req))->nrequests);
+		atomic_long_dec(&nfsi->nrequests);
 	}
 }
 
-- 
2.41.0