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Re: [Qemu-stable] [Qemu-devel] [PATCH] block: fix big write


From: Max Reitz
Subject: Re: [Qemu-stable] [Qemu-devel] [PATCH] block: fix big write
Date: Fri, 05 Dec 2014 18:03:34 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.2.0

On 2014-12-05 at 17:15, Ming Lei wrote:
From: Ming Lei <address@hidden>

QEMU block should have supported to read/write at most
0x7fffff * 512 bytes, unfortunately INT_MAX is used to check
bytes in both bdrv_co_do_writev() and bdrv_check_byte_request(),
so cause write failure if nr_sectors is equal or more
than 0x400000.

There are still other INT_MAX usages in block.c, and they might
need to change to UINT_MAX too in future, but at least
this patch's change can make SCSI WRITE SAME 16 workable.

Cc: address@hidden
Signed-off-by: Ming Lei <address@hidden>
---
  block.c |    4 ++--
  1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/block.c b/block.c
index a612594..ddc18c2 100644
--- a/block.c
+++ b/block.c
@@ -2607,7 +2607,7 @@ static int bdrv_check_byte_request(BlockDriverState *bs, 
int64_t offset,
  {
      int64_t len;
- if (size > INT_MAX) {
+    if (size > UINT_MAX) {
          return -EIO;
      }
@@ -3420,7 +3420,7 @@ static int coroutine_fn bdrv_co_do_writev(BlockDriverState *bs,
      int64_t sector_num, int nb_sectors, QEMUIOVector *qiov,
      BdrvRequestFlags flags)
  {
-    if (nb_sectors < 0 || nb_sectors > (INT_MAX >> BDRV_SECTOR_BITS)) {
+    if (nb_sectors < 0 || nb_sectors > (UINT_MAX >> BDRV_SECTOR_BITS)) {
          return -EINVAL;
      }

This is intentional so a byte length can be stored in an integer. This is a pretty bad design decision, but we have to live with it until we really fix the block layer regarding the type lengths are stored in.

Max



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