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-rw-r--r--drivers/char/random.c62
-rw-r--r--fs/ext4/inode.c3
2 files changed, 64 insertions, 1 deletions
diff --git a/drivers/char/random.c b/drivers/char/random.c
index d3beed084c0a..c2f7de9dc543 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -1732,6 +1732,56 @@ void get_random_bytes(void *buf, int nbytes)
}
EXPORT_SYMBOL(get_random_bytes);
+
+/*
+ * Each time the timer fires, we expect that we got an unpredictable
+ * jump in the cycle counter. Even if the timer is running on another
+ * CPU, the timer activity will be touching the stack of the CPU that is
+ * generating entropy..
+ *
+ * Note that we don't re-arm the timer in the timer itself - we are
+ * happy to be scheduled away, since that just makes the load more
+ * complex, but we do not want the timer to keep ticking unless the
+ * entropy loop is running.
+ *
+ * So the re-arming always happens in the entropy loop itself.
+ */
+static void entropy_timer(struct timer_list *t)
+{
+ credit_entropy_bits(&input_pool, 1);
+}
+
+/*
+ * If we have an actual cycle counter, see if we can
+ * generate enough entropy with timing noise
+ */
+static void try_to_generate_entropy(void)
+{
+ struct {
+ unsigned long now;
+ struct timer_list timer;
+ } stack;
+
+ stack.now = random_get_entropy();
+
+ /* Slow counter - or none. Don't even bother */
+ if (stack.now == random_get_entropy())
+ return;
+
+ timer_setup_on_stack(&stack.timer, entropy_timer, 0);
+ while (!crng_ready()) {
+ if (!timer_pending(&stack.timer))
+ mod_timer(&stack.timer, jiffies+1);
+ mix_pool_bytes(&input_pool, &stack.now, sizeof(stack.now));
+ schedule();
+ stack.now = random_get_entropy();
+ }
+
+ del_timer_sync(&stack.timer);
+ destroy_timer_on_stack(&stack.timer);
+ mix_pool_bytes(&input_pool, &stack.now, sizeof(stack.now));
+}
+
/*
* Wait for the urandom pool to be seeded and thus guaranteed to supply
* cryptographically secure random numbers. This applies to: the /dev/urandom
@@ -1746,7 +1796,17 @@ int wait_for_random_bytes(void)
{
if (likely(crng_ready()))
return 0;
- return wait_event_interruptible(crng_init_wait, crng_ready());
+
+ do {
+ int ret;
+ ret = wait_event_interruptible_timeout(crng_init_wait, crng_ready(), HZ);
+ if (ret)
+ return ret > 0 ? 0 : ret;
+
+ try_to_generate_entropy();
+ } while (!crng_ready());
+
+ return 0;
}
EXPORT_SYMBOL(wait_for_random_bytes);
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 123e3dee7733..516faa280ced 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -4551,6 +4551,7 @@ static int __ext4_get_inode_loc(struct inode *inode,
struct buffer_head *bh;
struct super_block *sb = inode->i_sb;
ext4_fsblk_t block;
+ struct blk_plug plug;
int inodes_per_block, inode_offset;
iloc->bh = NULL;
@@ -4639,6 +4640,7 @@ make_io:
* If we need to do any I/O, try to pre-readahead extra
* blocks from the inode table.
*/
+ blk_start_plug(&plug);
if (EXT4_SB(sb)->s_inode_readahead_blks) {
ext4_fsblk_t b, end, table;
unsigned num;
@@ -4669,6 +4671,7 @@ make_io:
get_bh(bh);
bh->b_end_io = end_buffer_read_sync;
submit_bh(REQ_OP_READ, REQ_META | REQ_PRIO, bh);
+ blk_finish_plug(&plug);
wait_on_buffer(bh);
if (!buffer_uptodate(bh)) {
EXT4_ERROR_INODE_BLOCK(inode, block,

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