drbd: Remove some fixed header size assumptions

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>

3 files changed, 35 insertions, 34 deletions

diff --git a/drivers/block/drbd/drbd_int.h b/drivers/block/drbd/drbd_int.h
index ccc374cc7eaa..cb16783e78df 100644
--- a/drivers/block/drbd/drbd_int.h
+++ b/drivers/block/drbd/drbd_int.h
@@ -543,19 +543,10 @@ struct p_delay_probe93 {
         u32     offset;  /* usecs the probe got sent after the reference time point */
 } __packed;
 
-/* one bitmap packet, including the p_header,
- * should fit within one _architecture independend_ page.
- * so we need to use the fixed size 4KiB page size
- * most architectures have used for a long time.
+/*
+ * Bitmap packets need to fit within a single page on the sender and receiver,
+ * so we are limited to 4 KiB (and not to PAGE_SIZE, which can be bigger).
  */
-#define BM_PACKET_PAYLOAD_BYTES (4096 - sizeof(struct p_header))
-#define BM_PACKET_WORDS (BM_PACKET_PAYLOAD_BYTES/sizeof(long))
-#define BM_PACKET_VLI_BYTES_MAX (4096 - sizeof(struct p_compressed_bm))
-#if (PAGE_SIZE < 4096)
-/* drbd_send_bitmap / receive_bitmap would break horribly */
-#error "PAGE_SIZE too small"
-#endif
-
 #define DRBD_SOCKET_BUFFER_SIZE 4096
 
 /**********************************************************************/
diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index e3dc84dcd67e..3ecbd4908cdc 100644
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -1100,8 +1100,9 @@ static void dcbp_set_pad_bits(struct p_compressed_bm *p, int n)
 }
 
 int fill_bitmap_rle_bits(struct drbd_conf *mdev,
-        struct p_compressed_bm *p,
-        struct bm_xfer_ctx *c)
+                         struct p_compressed_bm *p,
+                         unsigned int size,
+                         struct bm_xfer_ctx *c)
 {
         struct bitstream bs;
         unsigned long plain_bits;
@@ -1120,8 +1121,8 @@ int fill_bitmap_rle_bits(struct drbd_conf *mdev,
                 return 0; /* nothing to do. */
 
         /* use at most thus many bytes */
-        bitstream_init(&bs, p->code, BM_PACKET_VLI_BYTES_MAX, 0);
-        memset(p->code, 0, BM_PACKET_VLI_BYTES_MAX);
+        bitstream_init(&bs, p->code, size, 0);
+        memset(p->code, 0, size);
         /* plain bits covered in this code string */
         plain_bits = 0;
 
@@ -1203,11 +1204,11 @@ static int
 send_bitmap_rle_or_plain(struct drbd_conf *mdev, struct bm_xfer_ctx *c)
 {
         struct drbd_socket *sock = &mdev->tconn->data;
+        unsigned int header_size = drbd_header_size(mdev->tconn);
         struct p_compressed_bm *p = sock->sbuf;
-        unsigned long num_words;
         int len, err;
 
-        len = fill_bitmap_rle_bits(mdev, p, c);
+        len = fill_bitmap_rle_bits(mdev, p, DRBD_SOCKET_BUFFER_SIZE - sizeof(*p) /* FIXME */, c);
         if (len < 0)
                 return -EIO;
 
@@ -1224,9 +1225,14 @@ send_bitmap_rle_or_plain(struct drbd_conf *mdev, struct bm_xfer_ctx *c)
         } else {
                 /* was not compressible.
                  * send a buffer full of plain text bits instead. */
+                unsigned int data_size;
+                unsigned long num_words;
                 struct p_header *h = sock->sbuf;
-                num_words = min_t(size_t, BM_PACKET_WORDS, c->bm_words - c->word_offset);
-                len = num_words * sizeof(long);
+
+                data_size = DRBD_SOCKET_BUFFER_SIZE - header_size;
+                num_words = min_t(size_t, data_size / sizeof(unsigned long),
+                                  c->bm_words - c->word_offset);
+                len = num_words * sizeof(unsigned long);
                 if (len)
                         drbd_bm_get_lel(mdev, c->word_offset, num_words,
                                         (unsigned long *)h->payload);
@@ -1236,7 +1242,7 @@ send_bitmap_rle_or_plain(struct drbd_conf *mdev, struct bm_xfer_ctx *c)
                 c->bit_offset = c->word_offset * BITS_PER_LONG;
 
                 c->packets[1]++;
-                c->bytes[1] += sizeof(struct p_header80) + len;
+                c->bytes[1] += header_size + len;
 
                 if (c->bit_offset > c->bm_bits)
                         c->bit_offset = c->bm_bits;
@@ -2550,7 +2556,6 @@ int __init drbd_init(void)
 {
         int err;
 
-        BUILD_BUG_ON(sizeof(struct p_header80) != sizeof(struct p_header95));
         BUILD_BUG_ON(sizeof(struct p_connection_features) != 80);
 
         if (minor_count < DRBD_MINOR_COUNT_MIN || minor_count > DRBD_MINOR_COUNT_MAX) {
diff --git a/drivers/block/drbd/drbd_receiver.c b/drivers/block/drbd/drbd_receiver.c
index 40fe7199d5f7..74ed3ac263f3 100644
--- a/drivers/block/drbd/drbd_receiver.c
+++ b/drivers/block/drbd/drbd_receiver.c
@@ -3660,16 +3660,19 @@ static int receive_sync_uuid(struct drbd_tconn *tconn, struct packet_info *pi)
  * code upon failure.
  */
 static int
-receive_bitmap_plain(struct drbd_conf *mdev, unsigned int data_size,
+receive_bitmap_plain(struct drbd_conf *mdev, unsigned int size,
                      struct p_header *h, struct bm_xfer_ctx *c)
 {
         unsigned long *buffer = (unsigned long *)h->payload;
-        unsigned num_words = min_t(size_t, BM_PACKET_WORDS, c->bm_words - c->word_offset);
-        unsigned want = num_words * sizeof(long);
+        unsigned int data_size = DRBD_SOCKET_BUFFER_SIZE -
+                                 drbd_header_size(mdev->tconn);
+        unsigned int num_words = min_t(size_t, data_size / sizeof(unsigned long),
+                                       c->bm_words - c->word_offset);
+        unsigned int want = num_words * sizeof(unsigned long);
         int err;
 
-        if (want != data_size) {
-                dev_err(DEV, "%s:want (%u) != data_size (%u)\n", __func__, want, data_size);
+        if (want != size) {
+                dev_err(DEV, "%s:want (%u) != size (%u)\n", __func__, want, size);
                 return -EIO;
         }
         if (want == 0)
@@ -3796,11 +3799,13 @@ void INFO_bm_xfer_stats(struct drbd_conf *mdev,
                 const char *direction, struct bm_xfer_ctx *c)
 {
         /* what would it take to transfer it "plaintext" */
-        unsigned plain = sizeof(struct p_header) *
-                ((c->bm_words+BM_PACKET_WORDS-1)/BM_PACKET_WORDS+1)
-                + c->bm_words * sizeof(long);
-        unsigned total = c->bytes[0] + c->bytes[1];
-        unsigned r;
+        unsigned int header_size = drbd_header_size(mdev->tconn);
+        unsigned int data_size = DRBD_SOCKET_BUFFER_SIZE - header_size;
+        unsigned int plain =
+                header_size * (DIV_ROUND_UP(c->bm_words, data_size) + 1) +
+                c->bm_words * sizeof(unsigned long);
+        unsigned int total = c->bytes[0] + c->bytes[1];
+        unsigned int r;
 
         /* total can not be zero. but just in case: */
         if (total == 0)
@@ -3862,7 +3867,7 @@ static int receive_bitmap(struct drbd_tconn *tconn, struct packet_info *pi)
                          * and the feature is enabled! */
                         struct p_compressed_bm *p;
 
-                        if (pi->size > BM_PACKET_PAYLOAD_BYTES) {
+                        if (pi->size > DRBD_SOCKET_BUFFER_SIZE - drbd_header_size(tconn)) {
                                 dev_err(DEV, "ReportCBitmap packet too large\n");
                                 err = -EIO;
                                 goto out;
@@ -3885,7 +3890,7 @@ static int receive_bitmap(struct drbd_tconn *tconn, struct packet_info *pi)
                 }
 
                 c.packets[pi->cmd == P_BITMAP]++;
-                c.bytes[pi->cmd == P_BITMAP] += sizeof(struct p_header) + pi->size;
+                c.bytes[pi->cmd == P_BITMAP] += drbd_header_size(tconn) + pi->size;
 
                 if (err <= 0) {
                         if (err < 0)