On Sat, Jan 18, 2014 at 08:27:17PM +0000, Al Viro wrote: > Ouch^2: default_file_write_splice_write() keeps calling write_pipe_buf(), > which does this: > data = buf->ops->map(pipe, buf, 0); > ret = __kernel_write(sd->u.file, data + buf->offset, sd->len, &tmp); > buf->ops->unmap(pipe, buf, data); > IOW, ->write() (with whatever locks there might be) wrapped into > kmap_atomic()/kunmap_atomic(). And anybody can do that - just a splice to > file on procfs will hit that codepath... Or on 9p, for that matter, or > fat, or afs, or cifs, etc. s/kmap_atomic/kmap/, so it's not that disastrously bad (kmap_atomic might lose the mapping as soon as we block), but scarcity problem remains... -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
