[linux-cifs-client] read/write retry behavior with dead network/server/disconnected cable

[Steven French]

Shirish did some useful research today, confirming that there is one cifs 
write case (case d below) that needs more investigation in regards to 
retry behavior when the cable is unplugged (or network or server is down). 
 Cases a) and b) look fine. See below:

a) with hard option, read/write block forver but resume once the link is 
restored.

b) with forcedirectio, read/write block for approximately 30/50 seconds or 
so and then return with return code of -1 and errno set to 0x70  (112 
EHOSTDOWN).

c) with default options, read blocks for approximately 30 seconds or so 
and then returns without any error with return code of 0x0, read call 
keeps reading for 3 seconds and then blocks one
more time for approximately 30 seconds and then returns with return code 
of -1 and errno set to 0x70.  I do not know what it is reading (cached 
data) for three seconds without returning an 
error code.

d) with default option, write blocks for approximately 50 seconds and then 
keeps on writing every 10 seconds without any error.  I do not know what 
it is writing and where.


Steve French
Senior Software Engineer
Linux Technology Center - IBM Austin
phone: 512-838-2294
email: sfrench at-sign us dot ibm dot com