Fix bch2_super_write() alignment

We're about to switch to O_DIRECT only, which means we need to write
with proper alignment.

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

diff --git a/libbcachefs.c b/libbcachefs.c
index ec6b2727a8b33e4e7c862ada8adbe6a5a20f476d..36707654dc761113e21c54d8a51d1827a7ba3b71 100644 (file)
--- a/libbcachefs.c
+++ b/libbcachefs.c
@@ -342,6 +342,7 @@ struct bch_sb *bch2_format(struct bch_opt_strs      fs_opt_strs,
 void bch2_super_write(int fd, struct bch_sb *sb)
 {
        struct nonce nonce = { 0 };
+       unsigned bs = get_blocksize(fd);
 
        unsigned i;
        for (i = 0; i < sb->layout.nr_superblocks; i++) {
@@ -349,13 +350,22 @@ void bch2_super_write(int fd, struct bch_sb *sb)
 
                if (sb->offset == BCH_SB_SECTOR) {
                        /* Write backup layout */
-                       xpwrite(fd, &sb->layout, sizeof(sb->layout),
-                               BCH_SB_LAYOUT_SECTOR << 9,
+
+                       BUG_ON(bs > 4096);
+
+                       char *buf = aligned_alloc(bs, bs);
+                       xpread(fd, buf, bs, 4096 - bs);
+                       memcpy(buf + bs - sizeof(sb->layout),
+                              &sb->layout,
+                              sizeof(sb->layout));
+                       xpwrite(fd, buf, bs, 4096 - bs,
                                "backup layout");
+                       free(buf);
+
                }
 
                sb->csum = csum_vstruct(NULL, BCH_SB_CSUM_TYPE(sb), nonce, sb);
-               xpwrite(fd, sb, vstruct_bytes(sb),
+               xpwrite(fd, sb, round_up(vstruct_bytes(sb), bs),
                        le64_to_cpu(sb->offset) << 9,
                        "superblock");
        }