• Maxim Patlasov's avatar
    fuse: hold i_mutex in fuse_file_fallocate() · 14c14414
    Maxim Patlasov authored
    
    
    Changing size of a file on server and local update (fuse_write_update_size)
    should be always protected by inode->i_mutex. Otherwise a race like this is
    possible:
    
    1. Process 'A' calls fallocate(2) to extend file (~FALLOC_FL_KEEP_SIZE).
    fuse_file_fallocate() sends FUSE_FALLOCATE request to the server.
    2. Process 'B' calls ftruncate(2) shrinking the file. fuse_do_setattr()
    sends shrinking FUSE_SETATTR request to the server and updates local i_size
    by i_size_write(inode, outarg.attr.size).
    3. Process 'A' resumes execution of fuse_file_fallocate() and calls
    fuse_write_update_size(inode, offset + length). But 'offset + length' was
    obsoleted by ftruncate from previous step.
    
    Changed in v2 (thanks Brian and Anand for suggestions):
     - made relation between mutex_lock() and fuse_set_nowrite(inode) more
       explicit and clear.
     - updated patch description to use ftruncate(2) in example
    Signed-off-by: default avatarMaxim V. Patlasov <MPatlasov@parallels.com>
    Reviewed-by: default avatarBrian Foster <bfoster@redhat.com>
    Signed-off-by: default avatarMiklos Szeredi <mszeredi@suse.cz>
    14c14414
file.c 62.2 KB