fs: Align direct and unaligned read requests to blocksize boundary

[aravind-wdc]

For read requests which are direct and unaligned, zenfs fallsback on buffered reads. As a result, applications using direct reads could experience buffered reads and can also see a spike in kernel buffer usage. Align the read request size to the next blocksize boundary and issue direct reads for such requests.

Signed-off-by: Aravind Ramesh aravind.ramesh@wdc.com

[aravind-wdc]

This address the issue WDCZEN-22 in jira, where percona-myrocks experienced high kernel memory usage (~100gb) in bulk mode when doing direct reads.

[yhr]

@aravind-wdc : could you submit a PR to the V1 branch as well?

[yhr]

pushed manually