| Message ID | 50C70B4D.1000505@redhat.com |
|---|---|
| State | New |
| Headers | show |
On Tue, 2012-12-11 at 11:30 +0100, Kevin Wolf wrote: > Am 11.12.2012 10:58, schrieb Heinz Graalfs: > > Hi Kevin, > > > > I'm using the bdrv_pread() function during boot partition detection ... > > > > In detail: > > bdrv_pread() is called to read 32 bytes from a 2048 bytes formatted > > disk. This results in setting up a read of 512 bytes (1 sector > > multiplied by 512 current code in paio_submit()), which is wrong for a > > O_DIRECT opened file, and produces the error. > > So this sounds like the real problem: bdrv_pread/pwrite assume 512 byte > sectors. May it's better to fix it there instead of just fixing one code > path in one backend. > > In any case this patch as submitted is wrong as it overflows the buffer > passed to paio_submit. Test it with this patch: > > --- a/qemu-io.c > +++ b/qemu-io.c > @@ -1718,6 +1718,8 @@ static int openfile(char *name, int flags, int > growable) > bs = NULL; > return 1; > } > + > + bdrv_set_buffer_alignment(bs, 4096); > } > > return 0; > > > $ ./qemu-io -n -c 'read -p 0 512' /tmp/foo > read 512/512 bytes at offset 0 > 512 bytes, 1 ops; 0.0001 sec (3.727 MiB/sec and 7633.5878 ops/sec) > *** glibc detected *** ./qemu-io: double free or corruption (out): > 0x00007fa22349b000 *** > > Kevin > Kevin, I tried your fix and it solves the free error... Here is what I get: # lsdasd Bus-ID Status Name Device Type BlkSz Size Blocks ============================================================================== 0.0.37a1 active dasdb 94:4 ECKD 2048 6162MB 3155355 0.0.37a0 active dasdc 94:8 ECKD 512 3594MB 7362495 # ./qemu-io -c 'read -p 0 512' /dev/disk/by-path/ccw-0.0.37a0 read 512/512 bytes at offset 0 512 bytes, 1 ops; 0.0000 sec (7.512 MiB/sec and 15384.6154 ops/sec) # ./qemu-io -n -c 'read -p 0 512' /dev/disk/by-path/ccw-0.0.37a0 read 512/512 bytes at offset 0 512 bytes, 1 ops; 0.0005 sec (904.159 KiB/sec and 1808.3183 ops/sec) # ./qemu-io -c 'read -p 0 512' /dev/disk/by-path/ccw-0.0.37a1 read 512/512 bytes at offset 0 512 bytes, 1 ops; 0.0000 sec (7.288 MiB/sec and 14925.3731 ops/sec) # ./qemu-io -n -c 'read -p 0 512' /dev/disk/by-path/ccw-0.0.37a1 read failed: Invalid argument # Are you going to fix the rest in bdrv_pread/pwrite too? Heinz
--- a/qemu-io.c +++ b/qemu-io.c @@ -1718,6 +1718,8 @@ static int openfile(char *name, int flags, int growable) bs = NULL; return 1; } + + bdrv_set_buffer_alignment(bs, 4096); }