bcachefs: Fix buffered write path for generic/275

Per fstests generic/275, on -ENOSPC we're supposed write until the
filesystem is full - i.e. do a partial write instead of failing the full
write.

This is a partial fix for the buffered write path: we'll still fail on a
page boundary.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

diff --git a/fs/bcachefs/fs-io.c b/fs/bcachefs/fs-io.c
index b1d53290f6bac3f04a0073c81dfd049a719bcbac..49b0fb6522e7028e8a34aa7cb41b74882c308d25 100644 (file)
--- a/fs/bcachefs/fs-io.c
+++ b/fs/bcachefs/fs-io.c
@@ -1656,10 +1656,21 @@ static int __bch2_buffered_write(struct bch_inode_info *inode,
                                goto out;
                }
 
+               /*
+                * XXX: per POSIX and fstests generic/275, on -ENOSPC we're
+                * supposed to write as much as we have disk space for.
+                *
+                * On failure here we should still write out a partial page if
+                * we aren't completely out of disk space - we don't do that
+                * yet:
+                */
                ret = bch2_page_reservation_get(c, inode, page, &res,
                                                pg_offset, pg_len);
-               if (ret)
-                       goto out;
+               if (unlikely(ret)) {
+                       if (!reserved)
+                               goto out;
+                       break;
+               }
 
                reserved += pg_len;
        }
@@ -1668,10 +1679,10 @@ static int __bch2_buffered_write(struct bch_inode_info *inode,
                for (i = 0; i < nr_pages; i++)
                        flush_dcache_page(pages[i]);
 
-       while (copied < len) {
+       while (copied < reserved) {
                struct page *page = pages[(offset + copied) >> PAGE_SHIFT];
                unsigned pg_offset = (offset + copied) & (PAGE_SIZE - 1);
-               unsigned pg_len = min_t(unsigned, len - copied,
+               unsigned pg_len = min_t(unsigned, reserved - copied,
                                        PAGE_SIZE - pg_offset);
                unsigned pg_copied = copy_page_from_iter_atomic(page,
                                                pg_offset, pg_len, iter);