Re: [PATCH RESEND 1/2 block#for-linus] bio, fs: update READA and SWRITE to match the corresponding BIO_RW_* bits

Tejun Heo [off-list ref] writes:

Commit a82afdf (block: use the same failfast bits for bio and request)
moved BIO_RW_* bits around such that they match up with REQ_* bits.
Unfortunately, fs.h hard coded READ, WRITE, READA and SWRITE as 0, 1,
2 and 3, and expected them to match with BIO_RW_* bits.  READ/WRITE
didn't change but BIO_RW_AHEAD was moved to bit 4 instead of bit 1,
breaking READA and SWRITE.

This patch updates READA and SWRITE such that they match the BIO_RW_*
bits again.  A follow up patch will update the definitions to directly
use BIO_RW_* bits so that this kind of breakage won't happen again.

Stable: The offending commit a82afdf was released with v2.6.32, so
this patch should be applied to all kernels since then but it must
_NOT_ be applied to kernels earlier than that.

Would someone be so kind as to remind me how this problem manifests
itself?  I know I read this recently, but my memory and googling skills
are both failing me.  :(

Cheers,
Jeff