"Jeff Hostetler via GitGitGadget" <gitgitgadget@xxxxxxxxx> writes:
> +/*
> + * Use the name-hash to do a case-insensitive cache-entry lookup with
> + * the pathname and invalidate the cache-entry.
> + *
> + * Returns the number of cache-entries that we invalidated.
> + */
> +static size_t handle_using_name_hash_icase(
> + struct index_state *istate, const char *name)
> +{
> + struct cache_entry *ce = NULL;
> +
> + ce = index_file_exists(istate, name, strlen(name), 1);
> + if (!ce)
> + return 0;
> +
> + /*
> + * A case-insensitive search in the name-hash using the
> + * observed pathname found a cache-entry, so the observed path
> + * is case-incorrect. Invalidate the cache-entry and use the
> + * correct spelling from the cache-entry to invalidate the
> + * untracked-cache. Since we now have sparse-directories in
> + * the index, the observed pathname may represent a regular
> + * file or a sparse-index directory.
> + *
> + * Note that we should not have seen FSEvents for a
> + * sparse-index directory, but we handle it just in case.
> + *
> + * Either way, we know that there are not any cache-entries for
> + * children inside the cone of the directory, so we don't need to
> + * do the usual scan.
> + */
> + trace_printf_key(&trace_fsmonitor,
> + "fsmonitor_refresh_callback MAP: '%s' '%s'",
> + name, ce->name);
> +
> + untracked_cache_invalidate_trimmed_path(istate, ce->name, 0);
> + ce->ce_flags &= ~CE_FSMONITOR_VALID;
> + return 1;
> +}
You first ask the name-hash to turn the incoming "name" into the
case variant that we know about, i.e. ce->name, and use that to
access the untracked cache. Clever and makes sense. But if we have
ce->name, doesn't it mean the name is tracked? Do we find anything
useful to do in the untracked cache invalidation codepath in that
case?
An FSmonitor event with case-incorrect pathname for a directory may
not be this trivial, I presume, and I expect that is what the
remainder of this patch is about.
> +
> +/*
> + * Use the dir-name-hash to find the correct-case spelling of the
> + * directory. Use the canonical spelling to invalidate all of the
> + * cache-entries within the matching cone.
> + *
> + * Returns the number of cache-entries that we invalidated.
> + */
> +static size_t handle_using_dir_name_hash_icase(
> + struct index_state *istate, const char *name)
It is a bit unfortunate that here on the name-hash side we contrast
the two helper function variants as "dir-name" vs "name", while the
original handle_path side use "without_slash" vs "with_slash".
If I understand correctly, it is not like there are two distinct
hashes, "name-hash" vs "dir-name-hash". Both of these helpers use
the same "name-hash" mechanism, and this function differs from the
previous one in that it is about a directory, which is why it has
"dir" in its name. I wonder if we renamed the other one with
"nondir" in its name, and the other without_slash and with_slash
pair to match, e.g., handle_nondir_path() vs handle_dir_path(), or
something like that, the resulting names for these four functions
become easier to contrast and understand?
> +{
> + struct strbuf canonical_path = STRBUF_INIT;
> + int pos;
> + size_t len = strlen(name);
> + size_t nr_in_cone;
> +
> + if (name[len - 1] == '/')
> + len--;
> +
> + if (!index_dir_find(istate, name, len, &canonical_path))
> + return 0; /* name is untracked */
> +
> + if (!memcmp(name, canonical_path.buf, canonical_path.len)) {
> + strbuf_release(&canonical_path);
> + /*
> + * NEEDSWORK: Our caller already tried an exact match
> + * and failed to find one. They called us to do an
> + * ICASE match, so we should never get an exact match,
> + * so we could promote this to a BUG() here if we
> + * wanted to. It doesn't hurt anything to just return
> + * 0 and go on becaus we should never get here. Or we
> + * could just get rid of the memcmp() and this "if"
> + * clause completely.
> + */
> + return 0; /* should not happen */
> + }
"becaus" -> "because".
If we should never get here, having BUG("we should never get here")
would not hurt anything, either. On the other hand, silently
returning 0 will hide the bug under the carpet, and I am not sure it
is fair to call it "doesn't hurt anything".
> +
> + trace_printf_key(&trace_fsmonitor,
> + "fsmonitor_refresh_callback MAP: '%s' '%s'",
> + name, canonical_path.buf);
> +
> + /*
> + * The dir-name-hash only tells us the corrected spelling of
> + * the prefix. We have to use this canonical path to do a
> + * lookup in the cache-entry array so that we repeat the
> + * original search using the case-corrected spelling.
> + */
> + strbuf_addch(&canonical_path, '/');
> + pos = index_name_pos(istate, canonical_path.buf,
> + canonical_path.len);
> + nr_in_cone = handle_path_with_trailing_slash(
> + istate, canonical_path.buf, pos);
> + strbuf_release(&canonical_path);
> + return nr_in_cone;
> +}
Nice. Do we need to give this corrected name to help untracked
cache invalidation from the caller that called us?
> @@ -319,6 +416,19 @@ static void fsmonitor_refresh_callback(struct index_state *istate, char *name)
> else
> nr_in_cone = handle_path_without_trailing_slash(istate, name, pos);
>
> + /*
> + * If we did not find an exact match for this pathname or any
> + * cache-entries with this directory prefix and we're on a
> + * case-insensitive file system, try again using the name-hash
> + * and dir-name-hash.
> + */
> + if (!nr_in_cone && ignore_case) {
> + nr_in_cone = handle_using_name_hash_icase(istate, name);
> + if (!nr_in_cone)
> + nr_in_cone = handle_using_dir_name_hash_icase(
> + istate, name);
> + }
It might be interesting to learn how often we go through these
"fallback" code paths by tracing. Maybe it will become too noisy?
I dunno.
> if (nr_in_cone)
> trace_printf_key(&trace_fsmonitor,
> "fsmonitor_refresh_callback CNT: %d",
