On Tue, Dec 19, 2017 at 6:19 PM, Corinna Vinschen
wrote:
> On Dec 19 16:35, Ivan Kozik wrote:
>> From what I observe on Linux, it supports writing at any offset to the
>> block device because it does a read-modify-write behind the scenes,
>> with accompanying nasty overhead
On Tue, Dec 19, 2017 at 4:13 PM, Eric Blake wrote:
> Can block devices report an unaligned offset to lseek()? If not, then when
> writing an unaligned value to a block device, don't we have to do a
> read-modify-write of the larger aligned cluster, and then put lseek() back
> to the unaligned bou
On Tue, Dec 19, 2017 at 9:14 AM, Corinna Vinschen
wrote:
> Neither glibc nor FreeBSD show this behaviour. Keep in mind that stdio
> is designed for buffered I/O. What should happen, basically, is that a
> multiple of the stdio buffersize is written and the remainder is kept in
> the stdio buffer
Hello,
I have discovered that if you write 65536 + 1 bytes to a block device
in cygwin, the file position can become 65536 + 512.
With /dev/sdc as a throwaway USB block device:
(cygwin_write.c is pasted below)
# gcc -O2 -Wall -o cygwin_write cygwin_write.c
# ./cygwin_write /dev/sdc
66048
I am r
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