On 12/21/20 10:49 PM, Naohiro Aota wrote:
If more than one IO is issued for one file extent, these IO can be written to separate regions on a device. Since we cannot map one file extent to such a separate area, we need to follow the "one IO == one ordered extent" rule. The Normal buffered, uncompressed, not pre-allocated write path (used by cow_file_range()) sometimes does not follow this rule. It can write a part of an ordered extent when specified a region to write e.g., when its called from fdatasync(). Introduces a dedicated (uncompressed buffered) data write path for ZONED mode. This write path will CoW the region and write it at once. Signed-off-by: Naohiro Aota <naohiro.aota@xxxxxxx>
This means we'll write one page at a time, no coalescing of data pages. I'm not the one with zoned devices in production, but it might be worth fixing this in the future so you're not generating a billion bio's for large sequential data areas.
Reviewed-by: Josef Bacik <josef@xxxxxxxxxxxxxx> Thanks, Josef
