On 1/21/19 8:45 PM, Ashlie Martinez wrote:
I was working on porting parts of a file system crash consistency
checking tool called CrashMonkey [1] to linux kernels 4.9 and 4.14
when I noticed an inconsistency in how the bio->bi_opf field is
treated. According to the comments in /include/linux/blk_types.h, the
REQ_OP should be the upper bits in bi_opf, while the request flags
should be in the lower bits. In kernel 4.9, the accessor and setter
methods for this field appear to be correct. However, kernels 4.10+ do
not properly shift the REQ_OP argument up for either setting it or
getting it from bi_opf. Is this the intended behavior or is it a
mistake in how the code was written? Please note that I have not
checked all the releases between 4.9 and 5.0-rc3, but I know 4.10,
4.14, 4.15, and 5.0-rc3 contain the same or similar code for setting
bio->bi_opf.
Hi Ashlie,
Are you perhaps referring to commit ef295ecf090d ("block: better op and
flags encoding")? Have you noticed that that commit modified the
encoding such that the operation ends up in the lower 8 bits and the
flags in the upper 24 bits? That patch namely includes the following change:
+enum req_flag_bits {
+ __REQ_FAILFAST_DEV = /* no driver retries of device errors */
+ REQ_OP_BITS,
Bart.
