only a read lock on the inode, or without a lock at all (in case of prefetching) - it
is now using the cache_ref's lock to make sure it's retrieved only once and doesn't
waste/corrupts any memory.
- since that fix made it mandatory to fix write_chunk_into_cache() to not call pages_io()
while holding the cache_ref's lock (was a to-do item before), I changed it to make
that possible.
- It now also supports write-through caches in theory - as there is no way yet to tell
a cache to work this way.
- Optimized for the not so uncommon case of writing the last part of a file that is not
a multiple of the page size - it won't call pages_io() anymore then, but zero the rest
of the page directly.
- vm_page_write_modified() is now calling write_page() without holding the cache_ref's
lock as well.
The updated write_chunk_to_cache() is not so well tested, though, but appears to work
so far.
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@14006 a95241bf-73f2-0310-859d-f6bbb57e9c96