we already export mntauth() and mntversion(), so why not stop
being sneaky and just export mntattach() so bindmount() and
devshr can just call it directly with proper arguments being
checked.
we can also avoid handling #M attach specially in namec()
by having the devmnt's attach function do error(Enoattach).
to avoid double caching, attachimage() and setswapchan() clear
the CCACHE flag on the channel but this keeps the read ahread
state of the cache arround (until the chan gets closed), so also
call cclunk() to detach the mcp and free the read ahead state.
avoid the call to cread() when CCACHE flag is clear.
use the actual iounit returned from Ropen/Rcreate to chunk reads and writes
instead of c->mux->msize-IOHDRSZ.
dont preallocate the rpc buffers to msize, most 9p requests are rather small
(except Twrite of course). so we allocate the buffer on demand in mountio()
with some rounding to avoid frequent reallocations.
avoid malloc()/free() while holding mntalloc lock.
this changes devmnt adding mntrahread() function and some helpers
for it to do pipelined sequential read ahead for the mount cache.
basically, cread() calls mntrahread() with Mntrah structure and it
figures out if we where reading sequentially and if thats the case
issues reads of c->iounit size in advance.
the read ahead state (Mntrah) is kept in the mount cache so we can
handle (read ahead) cache invalidation in the presence of writes.
Tflush handling was wrong, we cannot respond to the old
request if we have not actually removed the req from the
in progress block queue.
when reads are issued concurrently, we have to set b->len
before the block is inserted into the inprogress list.
otherwise findblock() is unable to find it and no requests
can be queued on the block. this caused the same offset
to be downloaded multiple times.
set the errstr in getrange() so in case of an error, we dont
get some random previous error string.
as the Fgrp can be shared with other processes, we have to
recheck the fd index after locking the Fgrp in fdclose()
to make sure not to read beyond the bounds of the fd array.
using the user buffer has a race where the user can modify
the buffer from another process before it is copied into the cache.
this allows poisoning the cache for every file where the user
has read access.
instead, we update the cache from kernel memory.
*after* writing, the directory tree gets alphabetically sorted for
path table. this causes data to not be in the same order as it was
written causing seeks when taring up the filesystem.
so instead write the files in alphabetical order as well to better
match the directory sorting.
data on the disk is layed out sequentially and directory information
is at the end of the disk. we want to keep data and metadata separated
so that reading large sequential files will not evict the directory
information from the cache causing long seeks.
for that, we tag the clusters (an 8th for metadata, and the rest
for data) and getbuf() will only evict clusters of the same tag.
doing tests taring up 9front.iso shows the following:
lowering the cluster size back to 128k avoids over half the
reads. 837888 sectors read for 512k vs. 347712 sectors with
128k cluster size.
foo.c includes bar/bar.h, which includes "baz.h"; it wants bar/baz.h
meanwhile, it also includes meh/quux.h, which includes "baz.h"; it wants meh/baz.h
Wnode gets two new counters: txcount and txerror
and actrate pointer that will be between minrate
and maxrate.
driver should use actrate instead of maxrate for
transmission when it can provide error feedback.
when a driver detects a transmission failed, it calls
wifitxfail() with the original packet. wifitxfail() then
reduces wn->actrate.
every 256th packet, we optimistically increase wn->actrate
before transmitting.
