On Mon, 25 Feb 2019, Jason Harmening wrote:
On 2/25/19 9:46 PM, Bruce Evans wrote:
block_size <= PAGE_SIZE is very uncommon for ffs, even on systems with
large
pages.?? MINBSIZE is 4096 in ffs (except in my version, it is 512).?? The
default is 32768 in newfs.?? I consider this excessive and only use it for
file systems with many files larger than 1GB, but it is the most common
size.
It is larger than the large page size of 8192.
I think this is a case of filesystem logical block size vs. media sector
size, right? Here we're checking the devvp's block size, which I think
should correspond to the sector size. I'd expect cases of that being
greater than PAGE_SIZE to be uncommon, in fact geli warns when that is the
case. I probably should've made that clearer in the commit message.
Yes, I missed that you are checking devvp. ffs_getpages() also checks
devvp.
So the bug has nothing to do with file system logical (fragment) or i/o
(block) block size's, except file systems themselves won't work unless
their i/o size is a multiple of the underlying devices (sector) i/o size.
Are there physical disk with sector size > PAGE_SIZE now? It is easy to
create virtual (md) disks with sector size > PAGE_SIZE, and this may even
be useful for avoiding the related problem of having to access large fs
blocks to do i/o to small md sectors. I think it is best to use PAGE_SIZE
blocks in all layers and sometimes combine these into clusters.
Bruce
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