diff options
| -rw-r--r-- | drivers/char/random.c | 62 | ||||
| -rw-r--r-- | fs/ext4/inode.c | 3 |
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, |