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Diffstat (limited to 'docs')
| -rw-r--r-- | docs/design.md | 30 |
1 files changed, 24 insertions, 6 deletions
diff --git a/docs/design.md b/docs/design.md index dda10a6..8387a4d 100644 --- a/docs/design.md +++ b/docs/design.md @@ -104,13 +104,31 @@ negotiating. Every table is sized at comptime by `fs.Options`: `fid_capacity` (256), `slot_capacity` (32), `park_data_max` (128), `name_capacity` (28, at most -255) and `username_capacity` (28); the defaults are the editor's, except the -name capacity, which is the board's. `msize_min` (217) is the smallest -negotiable msize, one full Rwalk. Create, remove, auth, attaching a named -tree and any wstat other than a zero-length truncation are refused. Rerror -strings are the ones Linux v9fs maps back to errnos (`fs.errString`). The +255; zero keeps no names, a stat's name is then the one its getattr +answers and the backend judges name lengths), `username_capacity` (28) and +`fid_index` (off: an open-addressing index from fid number to slot, two +bytes per bucket, for tables of thousands of fids; `InitOptions.seed` +salts it); the defaults are the editor's, except the name capacity, which +is the board's. `msize_min` (217) is the smallest negotiable msize, one +full Rwalk. Auth and attaching a named tree are refused, and so are +create, remove and any wstat other than a zero-length truncation unless +the backend declares the feature: a backend may carry `pub const features: +fs.Features` naming `create` (Tcreate becomes an `open` with `create`, +`data` the name, `perm` and `omode`, answered with the new node's `attr` +and handle), `remove` (Tremove, and ORCLOSE on clunk or hangup, become a +`release` with `remove`; its error is the Rremove's), `wstat` (a Twstat +becomes a `setattr` whose `set` names the changed fields: `data` the new +name, `perm`, `mtime`, `length`; the fields the engine owns must be "don't +care") and `references` (every lookup result, "." and a fid clone +included, is a reference the backend gets exactly one `release` for, with +`opened` telling whether an open handle goes with it). An `Attr` may add +a qid `version`, `atime`, a qid `path` distinct from the node, and the +append-only and exclusive-use bits; a reply's `ename` replaces +`errString(errno)` as the Rerror text. Rerror strings the engine emits on +its own are the ones Linux v9fs maps back to errnos (`fs.errString`). The engine allocates nothing and makes no OS calls; a session is `push()`, -`retry()`, `next()`, `reply()`, `output()`, `wrote()`. +`retry()`, `next()`, `reply()`, `output()`, `wrote()`; `fidCount()` counts +the fids held. # Related programs |