[bug report] bcachefs: no checking for bch2_seek_pagecache_hole()

[Dan Carpenter]

Hello Kent Overstreet,

The patch e0750d947352: "bcachefs: Initial commit" from Mar 16, 2017
(linux-next), leads to the following Smatch static checker warning:

        fs/bcachefs/fs-io.c:1013 bch2_seek_hole()
        warn: error code type promoted to positive: 'next_hole'

fs/bcachefs/fs-io.c
    977 static loff_t bch2_seek_hole(struct file *file, u64 offset)
    978 {
    979         struct bch_inode_info *inode = file_bch_inode(file);
    980         struct bch_fs *c = inode->v.i_sb->s_fs_info;
    981         struct btree_trans *trans;
    982         struct btree_iter iter;
    983         struct bkey_s_c k;
    984         subvol_inum inum = inode_inum(inode);
    985         u64 isize, next_hole = MAX_LFS_FILESIZE;
    986         u32 snapshot;
    987         int ret;
    988 
    989         isize = i_size_read(&inode->v);
    990         if (offset >= isize)
    991                 return -ENXIO;
    992 
    993         trans = bch2_trans_get(c);
    994 retry:
    995         bch2_trans_begin(trans);
    996 
    997         ret = bch2_subvolume_get_snapshot(trans, inum.subvol, 
&snapshot);
    998         if (ret)
    999                 goto err;
    1000 
    1001         for_each_btree_key_norestart(trans, iter, BTREE_ID_extents,
    1002                            SPOS(inode->v.i_ino, offset >> 9, snapshot),
    1003                            BTREE_ITER_SLOTS, k, ret) {
    1004                 if (k.k->p.inode != inode->v.i_ino) {
    1005                         next_hole = bch2_seek_pagecache_hole(&inode->v,
    1006                                         offset, MAX_LFS_FILESIZE, 0, 
false);
    1007                         break;
    1008                 } else if (!bkey_extent_is_data(k.k)) {
    1009                         next_hole = bch2_seek_pagecache_hole(&inode->v,
    1010                                         max(offset, 
bkey_start_offset(k.k) << 9),
    1011                                         k.k->p.offset << 9, 0, false);
    1012 

bch2_seek_pagecache_hole returns llof_t.  Negatives on error.  This code
has no error checking?

--> 1013                         if (next_hole < k.k->p.offset << 9)
    1014                                 break;
    1015                 } else {
    1016                         offset = max(offset, bkey_start_offset(k.k) << 
9);
    1017                 }
    1018         }
    1019         bch2_trans_iter_exit(trans, &iter);
    1020 err:
    1021         if (bch2_err_matches(ret, BCH_ERR_transaction_restart))
    1022                 goto retry;
    1023 
    1024         bch2_trans_put(trans);
    1025         if (ret)
    1026                 return ret;
    1027 
    1028         if (next_hole > isize)
    1029                 next_hole = isize;
    1030 
    1031         return vfs_setpos(file, next_hole, MAX_LFS_FILESIZE);
    1032 }

regards,
dan carpenter