st: implement tape statistics
authorSeymour, Shane M <shane.seymour@hp.com>
Wed, 6 May 2015 01:37:20 +0000 (01:37 +0000)
committerJames Bottomley <JBottomley@Odin.com>
Tue, 2 Jun 2015 15:03:25 +0000 (08:03 -0700)
commit05545c92db9637318a98d3d59d400beb819decc7
tree56c911568dd7dd6507aac24f7c8c90b657f7bda0
parentba929992522b6d1f866b7021bc50da66f8fdd743
st: implement tape statistics

This patch implements tape statistics in the st module via
sysfs. Current no statistics are available for tape I/O and there
is no easy way to reuse the block layer statistics for tape
as tape is a character device and does not have perform I/O in
sector sized chunks (the size of the data written to tape
can change). For tapes we also need extra stats related to
things like tape movement (via other I/O).

There have been multiple end users requesting statistics
including AT&T (and some HP customers who have not given
permission to be named). It is impossible for them
to investigate any issues related to tape performance
in a non-invasive way.

[jejb: eliminate PRId64]
Signed-off-by: Shane Seymour <shane.seymour@hp.com>
Tested-by: Shane Seymour <shane.seymour@hp.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: James Bottomley <JBottomley@Odin.com>
Documentation/ABI/testing/sysfs-class-scsi_tape [new file with mode: 0644]
Documentation/scsi/st.txt
drivers/scsi/st.c
drivers/scsi/st.h