Re: [PATCH v2 14/16] fsmonitor: support case-insensitive events
On Fri, Feb 23, 2024 at 03:18:18AM +0000, Jeff Hostetler via GitGitGadget wrote:
Show 119 quoted lines
> From: Jeff Hostetler <jeffhostetler@github.com>
>
> Teach fsmonitor_refresh_callback() to handle case-insensitive
> lookups if case-sensitive lookups fail on case-insensitive systems.
> This can cause 'git status' to report stale status for files if there
> are case issues/errors in the worktree.
>
> The FSMonitor daemon sends FSEvents using the observed spelling
> of each pathname. On case-insensitive file systems this may be
> different than the expected case spelling.
>
> The existing code uses index_name_pos() to find the cache-entry for
> the pathname in the FSEvent and clear the CE_FSMONITOR_VALID bit so
> that the worktree scan/index refresh will revisit and revalidate the
> path.
>
> On a case-insensitive file system, the exact match lookup may fail
> to find the associated cache-entry. This causes status to think that
> the cached CE flags are correct and skip over the file.
>
> Update event handling to optionally use the name-hash and dir-name-hash
> if necessary.
>
> Signed-off-by: Jeff Hostetler <jeffhostetler@github.com>
> ---
> fsmonitor.c | 110 ++++++++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 110 insertions(+)
>
> diff --git a/fsmonitor.c b/fsmonitor.c
> index 739ddbf7aca..ac638a61c00 100644
> --- a/fsmonitor.c
> +++ b/fsmonitor.c
> @@ -5,6 +5,7 @@
> #include "ewah/ewok.h"
> #include "fsmonitor.h"
> #include "fsmonitor-ipc.h"
> +#include "name-hash.h"
> #include "run-command.h"
> #include "strbuf.h"
> #include "trace2.h"
> @@ -186,6 +187,102 @@ static int query_fsmonitor_hook(struct repository *r,
> static size_t handle_path_with_trailing_slash(
> struct index_state *istate, const char *name, int pos);
>
> +/*
> + * 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;
> +}
> +
> +/*
> + * 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)
> +{
> + 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 */In very very theory, there may be a race-condition,
when a directory is renamed very fast, more than once.
I don't think, that the "it did not match exactly, but
now it matches" is a problem.
Question: Does it make sense to just remove this ?
And, may be, find out that the "corrected spelling (tm)"
of "DIR1" is not "dir1", neither "Dir1", but, exactly, "DIR1" ?
Would that be a problem ?
Show 48 quoted lines
> + }
> +
> + 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;
> +}
> +
> /*
> * The daemon sent an observed pathname without a trailing slash.
> * (This is the normal case.) We do not know if it is a tracked or
> @@ -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);
> + }
> +
> if (nr_in_cone)
> trace_printf_key(&trace_fsmonitor,
> "fsmonitor_refresh_callback CNT: %d",
> --
> gitgitgadget
>
>Torsten Bögershausen <tboegi@web.de>