In getblk()( in buffer.c ), there are just two "return" statement:
if (bh) {
if (!buffer_dirty(bh)) {
if (buffer_uptodate(bh)) //最近访问过,如果不脏,且uptodate,放入表末尾
put_last_lru(bh);
bh->b_flushtime = 0;
}
return bh;
^^^^^^^^^^
}
and
if( !bh )
goto refill;
// bh can not be NULL now
....
return bh;
^^^^^^^^
So it can not return NULL.
But in block_read of block_dev.c，it assumes getblk() can return
NULL， and in this case it will copy zero to user space "buf".
Can anyone tell me when getblk() will return NULL?
Many thanks,
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