[v2,3/5] fsmonitor: config settings are repository-specific

Commit Message

Jeff Hostetler Oct. 7, 2021, 1:52 p.m. UTC

From: Jeff Hostetler <[e-mail]>

Move FSMonitor config settings to a new `struct fsmonitor_settings`
structure.  Add a lazily-loaded pointer to `struct repo_settings`.
Create `fsm_settings__get_*()` getters to lazily look up fsmonitor-
related config settings.

Get rid of the `core_fsmonitor` global variable, and add support for
the new `core.useBuiltinFSMonitor` config setting.  Move config code
to lookup the existing `core.fsmonitor` value to `fsmonitor-settings.[ch]`.

The `core_fsmonitor` global variable was used to store the pathname to
the FSMonitor hook and it was used as a boolean to see if FSMonitor
was enabled.  This dual usage will lead to confusion when we add
support for a builtin FSMonitor based on IPC, since the builtin
FSMonitor doesn't need the hook pathname.

Replace the boolean usage with an `enum fsmonitor_mode` to represent
the state of FSMonitor.  And only set the pathname when in HOOK mode.

Signed-off-by: Jeff Hostetler <[e-mail]>
---
 Makefile               |  1 +
 builtin/update-index.c | 19 +++++++--
 cache.h                |  1 -
 config.c               | 14 ------
 config.h               |  1 -
 environment.c          |  1 -
 fsmonitor-settings.c   | 97 ++++++++++++++++++++++++++++++++++++++++++
 fsmonitor-settings.h   | 21 +++++++++
 fsmonitor.c            | 63 ++++++++++++++++-----------
 fsmonitor.h            | 18 ++++++--
 repo-settings.c        |  2 +
 repository.h           |  3 ++
 t/README               |  4 +-
 13 files changed, 194 insertions(+), 51 deletions(-)
 create mode 100644 fsmonitor-settings.c
 create mode 100644 fsmonitor-settings.h

Comments

Ævar Arnfjörð Bjarmason Oct. 7, 2021, 4:59 p.m. UTC | #1

On Thu, Oct 07 2021, Jeff Hostetler via GitGitGadget wrote:

Good to see this move forward!

This bit:

> --- a/repo-settings.c
> +++ b/repo-settings.c
> @@ -20,6 +20,8 @@ void prepare_repo_settings(struct repository *r)
>  	if (r->settings.initialized++)
>  		return;
>  
> +	r->settings.fsmonitor = NULL; /* lazy loaded */
> +
>  	/* Defaults */
>  	r->settings.index_version = -1;
>  	r->settings.core_untracked_cache = UNTRACKED_CACHE_KEEP;
> diff --git a/repository.h b/repository.h

Is carried forward from v1, but with 3050b6dfc75 (repo-settings.c:
simplify the setup, 2021-09-21) isn't needed. It's init'd to 0/NULL
already, but was -1 before.

So this hunk can go, and its presence makes for confusing reading
without that history, is it set before somehow? No, just working around
older code that's no longer there.

But also: For untracked_cache_setting and fetch_negotiation_setting
we've got an embedded enum in the struct, but this...

> index a057653981c..89a1873ade7 100644
> --- a/repository.h
> +++ b/repository.h
> @@ -4,6 +4,7 @@
>  #include "path.h"
>  
>  struct config_set;
> +struct fsmonitor_settings;
>  struct git_hash_algo;
>  struct index_state;
>  struct lock_file;
> @@ -34,6 +35,8 @@ struct repo_settings {
>  	int command_requires_full_index;
>  	int sparse_index;
>  
> +	struct fsmonitor_settings *fsmonitor; /* lazy loaded */
> +
>  	int index_version;
>  	enum untracked_cache_setting core_untracked_cache;
>  

Is a pointer to a struct that has an "enum fsmonitor_mode mode", and the
code in fsmonitor-settings.c seems to be repeating the patterns we had
in repo-settings.c pre-3050b6dfc75, e.g. checking whether a bool config
variable exists *and* is true, v.s. checking if it exists (presumably an
explicit false wants to override something).

I haven't looked carefully, but between that & the "char *hook_path"
being something that'll need to be made to use Emily's hook config
series sooner than later, can't we read/setup the initial config in
"repo_cfg_bool"?

The relevant commit message just says:

    Move FSMonitor config settings to a new `struct fsmonitor_settings`
    structure.  Add a lazily-loaded pointer to `struct repo_settings`.
    Create `fsm_settings__get_*()` getters to lazily look up fsmonitor-
    related config settings.[...]

Which I think can be paraphrased as "Add scaffolding to repo-settings.c
but do config loading differently than everything there (lazily),
because...", except the "because" is missing :)

Jeff Hostetler Oct. 8, 2021, 8:36 p.m. UTC | #2

On 10/7/21 12:59 PM, Ævar Arnfjörð Bjarmason wrote:
> 
> On Thu, Oct 07 2021, Jeff Hostetler via GitGitGadget wrote:
> 
> Good to see this move forward!
> 
> This bit:
> 
>> --- a/repo-settings.c
>> +++ b/repo-settings.c
>> @@ -20,6 +20,8 @@ void prepare_repo_settings(struct repository *r)
>>   	if (r->settings.initialized++)
>>   		return;
>>   
>> +	r->settings.fsmonitor = NULL; /* lazy loaded */
>> +
>>   	/* Defaults */
>>   	r->settings.index_version = -1;
>>   	r->settings.core_untracked_cache = UNTRACKED_CACHE_KEEP;
>> diff --git a/repository.h b/repository.h
> 
> Is carried forward from v1, but with 3050b6dfc75 (repo-settings.c:
> simplify the setup, 2021-09-21) isn't needed. It's init'd to 0/NULL
> already, but was -1 before.
> 
> So this hunk can go, and its presence makes for confusing reading
> without that history, is it set before somehow? No, just working around
> older code that's no longer there.

Um, yeah, if the structure is now zero-filled on init
rather than the weird -1, then we don't need this here.
I'll remove in my next version.  Thanks!


> 
> But also: For untracked_cache_setting and fetch_negotiation_setting
> we've got an embedded enum in the struct, but this...
> 
>> index a057653981c..89a1873ade7 100644
>> --- a/repository.h
>> +++ b/repository.h
>> @@ -4,6 +4,7 @@
>>   #include "path.h"
>>   
>>   struct config_set;
>> +struct fsmonitor_settings;
>>   struct git_hash_algo;
>>   struct index_state;
>>   struct lock_file;
>> @@ -34,6 +35,8 @@ struct repo_settings {
>>   	int command_requires_full_index;
>>   	int sparse_index;
>>   
>> +	struct fsmonitor_settings *fsmonitor; /* lazy loaded */
>> +
>>   	int index_version;
>>   	enum untracked_cache_setting core_untracked_cache;
>>   
> 
> Is a pointer to a struct that has an "enum fsmonitor_mode mode", and the
> code in fsmonitor-settings.c seems to be repeating the patterns we had
> in repo-settings.c pre-3050b6dfc75, e.g. checking whether a bool config
> variable exists *and* is true, v.s. checking if it exists (presumably an
> explicit false wants to override something).

My usage is a little more complicated because the historical value
had double duty.  And I only want to set the hook value when not
using the builtin and when the repo itself is compatible with being
monitored.  Later in the series we'll disallow remote worktrees,
for example.  I wanted to hide some of those details in my
fsmonitor-settings.c and keep them out of repo-settings.c.  And
to avoid paying for that when not needed, I made is a lazy-load
and hid the values behind an opaque type with access functions.


> 
> I haven't looked carefully, but between that & the "char *hook_path"
> being something that'll need to be made to use Emily's hook config
> series sooner than later, can't we read/setup the initial config in
> "repo_cfg_bool"?

It's been a while since I looked at Emily's series. I'll have to
revisit that later.  I do wonder if the existing fsmonitor hook
is in the same class as the other hooks or whether it is a one-off
and should be separate, but again I need to review that work first.

> 
> The relevant commit message just says:
> 
>      Move FSMonitor config settings to a new `struct fsmonitor_settings`
>      structure.  Add a lazily-loaded pointer to `struct repo_settings`.
>      Create `fsm_settings__get_*()` getters to lazily look up fsmonitor-
>      related config settings.[...]
> 
> Which I think can be paraphrased as "Add scaffolding to repo-settings.c
> but do config loading differently than everything there (lazily),
> because...", except the "because" is missing :)
> 

Let me reword the commit message and try to explain what I was
going for.  Thanks!

Jeff

Patch

diff --git a/Makefile b/Makefile
index d51fd8b33ce..29ed7c4aba6 100644
--- a/Makefile
+++ b/Makefile
@@ -898,6 +898,7 @@  LIB_OBJS += fmt-merge-msg.o
 LIB_OBJS += fsck.o
 LIB_OBJS += fsmonitor.o
 LIB_OBJS += fsmonitor-ipc.o
+LIB_OBJS += fsmonitor-settings.o
 LIB_OBJS += gettext.o
 LIB_OBJS += gpg-interface.o
 LIB_OBJS += graph.o
diff --git a/builtin/update-index.c b/builtin/update-index.c
index 187203e8bb5..79db3ff37e2 100644
--- a/builtin/update-index.c
+++ b/builtin/update-index.c
@@ -1214,14 +1214,25 @@  int cmd_update_index(int argc, const char **argv, const char *prefix)
 	}
 
 	if (fsmonitor > 0) {
-		if (git_config_get_fsmonitor() == 0)
+		enum fsmonitor_mode fsm_mode = fsm_settings__get_mode(r);
+
+		if (fsm_mode == FSMONITOR_MODE_DISABLED) {
+			warning(_("core.useBuiltinFSMonitor is unset; "
+				"set it if you really want to enable the "
+				"builtin fsmonitor"));
 			warning(_("core.fsmonitor is unset; "
-				"set it if you really want to "
-				"enable fsmonitor"));
+				"set it if you really want to enable the "
+				"hook-based fsmonitor"));
+		}
 		add_fsmonitor(&the_index);
 		report(_("fsmonitor enabled"));
 	} else if (!fsmonitor) {
-		if (git_config_get_fsmonitor() == 1)
+		enum fsmonitor_mode fsm_mode = fsm_settings__get_mode(r);
+		if (fsm_mode == FSMONITOR_MODE_IPC)
+			warning(_("core.useBuiltinFSMonitor is set; "
+				"remove it if you really want to "
+				"disable fsmonitor"));
+		if (fsm_mode == FSMONITOR_MODE_HOOK)
 			warning(_("core.fsmonitor is set; "
 				"remove it if you really want to "
 				"disable fsmonitor"));
diff --git a/cache.h b/cache.h
index d092820c943..8f4e3c8bd1d 100644
--- a/cache.h
+++ b/cache.h
@@ -989,7 +989,6 @@  extern int core_preload_index;
 extern int precomposed_unicode;
 extern int protect_hfs;
 extern int protect_ntfs;
-extern const char *core_fsmonitor;
 
 extern int core_apply_sparse_checkout;
 extern int core_sparse_checkout_cone;
diff --git a/config.c b/config.c
index 2dcbe901b6b..6b6e9cacac3 100644
--- a/config.c
+++ b/config.c
@@ -2502,20 +2502,6 @@  int git_config_get_max_percent_split_change(void)
 	return -1; /* default value */
 }
 
-int git_config_get_fsmonitor(void)
-{
-	if (git_config_get_pathname("core.fsmonitor", &core_fsmonitor))
-		core_fsmonitor = getenv("GIT_TEST_FSMONITOR");
-
-	if (core_fsmonitor && !*core_fsmonitor)
-		core_fsmonitor = NULL;
-
-	if (core_fsmonitor)
-		return 1;
-
-	return 0;
-}
-
 int git_config_get_index_threads(int *dest)
 {
 	int is_bool, val;
diff --git a/config.h b/config.h
index f119de01309..69d733824a0 100644
--- a/config.h
+++ b/config.h
@@ -610,7 +610,6 @@  int git_config_get_pathname(const char *key, const char **dest);
 int git_config_get_index_threads(int *dest);
 int git_config_get_split_index(void);
 int git_config_get_max_percent_split_change(void);
-int git_config_get_fsmonitor(void);
 
 /* This dies if the configured or default date is in the future */
 int git_config_get_expiry(const char *key, const char **output);
diff --git a/environment.c b/environment.c
index 9da7f3c1a19..68f90632245 100644
--- a/environment.c
+++ b/environment.c
@@ -82,7 +82,6 @@  int protect_hfs = PROTECT_HFS_DEFAULT;
 #define PROTECT_NTFS_DEFAULT 1
 #endif
 int protect_ntfs = PROTECT_NTFS_DEFAULT;
-const char *core_fsmonitor;
 
 /*
  * The character that begins a commented line in user-editable file
diff --git a/fsmonitor-settings.c b/fsmonitor-settings.c
new file mode 100644
index 00000000000..2770266f5ee
--- /dev/null
+++ b/fsmonitor-settings.c
@@ -0,0 +1,97 @@ 
+#include "cache.h"
+#include "config.h"
+#include "repository.h"
+#include "fsmonitor-settings.h"
+
+/*
+ * We keep this structure defintion private and have getters
+ * for all fields so that we can lazy load it as needed.
+ */
+struct fsmonitor_settings {
+	enum fsmonitor_mode mode;
+	char *hook_path;
+};
+
+void fsm_settings__set_ipc(struct repository *r)
+{
+	struct fsmonitor_settings *s = r->settings.fsmonitor;
+
+	s->mode = FSMONITOR_MODE_IPC;
+}
+
+void fsm_settings__set_hook(struct repository *r, const char *path)
+{
+	struct fsmonitor_settings *s = r->settings.fsmonitor;
+
+	s->mode = FSMONITOR_MODE_HOOK;
+	s->hook_path = strdup(path);
+}
+
+void fsm_settings__set_disabled(struct repository *r)
+{
+	struct fsmonitor_settings *s = r->settings.fsmonitor;
+
+	s->mode = FSMONITOR_MODE_DISABLED;
+	FREE_AND_NULL(s->hook_path);
+}
+
+static int check_for_ipc(struct repository *r)
+{
+	int value;
+
+	if (!repo_config_get_bool(r, "core.usebuiltinfsmonitor", &value) &&
+	    value) {
+		fsm_settings__set_ipc(r);
+		return 1;
+	}
+
+	return 0;
+}
+
+static int check_for_hook(struct repository *r)
+{
+	const char *const_str;
+
+	if (repo_config_get_pathname(r, "core.fsmonitor", &const_str))
+		const_str = getenv("GIT_TEST_FSMONITOR");
+
+	if (const_str && *const_str) {
+		fsm_settings__set_hook(r, const_str);
+		return 1;
+	}
+
+	return 0;
+}
+
+static void lookup_fsmonitor_settings(struct repository *r)
+{
+	struct fsmonitor_settings *s;
+
+	CALLOC_ARRAY(s, 1);
+
+	r->settings.fsmonitor = s;
+
+	if (check_for_ipc(r))
+		return;
+
+	if (check_for_hook(r))
+		return;
+
+	fsm_settings__set_disabled(r);
+}
+
+enum fsmonitor_mode fsm_settings__get_mode(struct repository *r)
+{
+	if (!r->settings.fsmonitor)
+		lookup_fsmonitor_settings(r);
+
+	return r->settings.fsmonitor->mode;
+}
+
+const char *fsm_settings__get_hook_path(struct repository *r)
+{
+	if (!r->settings.fsmonitor)
+		lookup_fsmonitor_settings(r);
+
+	return r->settings.fsmonitor->hook_path;
+}
diff --git a/fsmonitor-settings.h b/fsmonitor-settings.h
new file mode 100644
index 00000000000..50b29234616
--- /dev/null
+++ b/fsmonitor-settings.h
@@ -0,0 +1,21 @@ 
+#ifndef FSMONITOR_SETTINGS_H
+#define FSMONITOR_SETTINGS_H
+
+struct repository;
+
+enum fsmonitor_mode {
+	FSMONITOR_MODE_DISABLED = 0,
+	FSMONITOR_MODE_HOOK = 1, /* core.fsmonitor */
+	FSMONITOR_MODE_IPC = 2,  /* core.useBuiltinFSMonitor */
+};
+
+void fsm_settings__set_ipc(struct repository *r);
+void fsm_settings__set_hook(struct repository *r, const char *path);
+void fsm_settings__set_disabled(struct repository *r);
+
+enum fsmonitor_mode fsm_settings__get_mode(struct repository *r);
+const char *fsm_settings__get_hook_path(struct repository *r);
+
+struct fsmonitor_settings;
+
+#endif /* FSMONITOR_SETTINGS_H */
diff --git a/fsmonitor.c b/fsmonitor.c
index ec4c46407c5..63174630c0e 100644
--- a/fsmonitor.c
+++ b/fsmonitor.c
@@ -3,6 +3,7 @@ 
 #include "dir.h"
 #include "ewah/ewok.h"
 #include "fsmonitor.h"
+#include "fsmonitor-ipc.h"
 #include "run-command.h"
 #include "strbuf.h"
 
@@ -148,15 +149,18 @@  void write_fsmonitor_extension(struct strbuf *sb, struct index_state *istate)
 /*
  * Call the query-fsmonitor hook passing the last update token of the saved results.
  */
-static int query_fsmonitor(int version, const char *last_update, struct strbuf *query_result)
+static int query_fsmonitor_hook(struct repository *r,
+				int version,
+				const char *last_update,
+				struct strbuf *query_result)
 {
 	struct child_process cp = CHILD_PROCESS_INIT;
 	int result;
 
-	if (!core_fsmonitor)
+	if (fsm_settings__get_mode(r) != FSMONITOR_MODE_HOOK)
 		return -1;
 
-	strvec_push(&cp.args, core_fsmonitor);
+	strvec_push(&cp.args, fsm_settings__get_hook_path(r));
 	strvec_pushf(&cp.args, "%d", version);
 	strvec_pushf(&cp.args, "%s", last_update);
 	cp.use_shell = 1;
@@ -238,17 +242,28 @@  void refresh_fsmonitor(struct index_state *istate)
 	struct strbuf last_update_token = STRBUF_INIT;
 	char *buf;
 	unsigned int i;
+	struct repository *r = istate->repo ? istate->repo : the_repository;
+	enum fsmonitor_mode fsm_mode = fsm_settings__get_mode(r);
 
-	if (!core_fsmonitor || istate->fsmonitor_has_run_once)
+	if (fsm_mode <= FSMONITOR_MODE_DISABLED ||
+	    istate->fsmonitor_has_run_once)
 		return;
 
-	hook_version = fsmonitor_hook_version();
-
 	istate->fsmonitor_has_run_once = 1;
 
 	trace_printf_key(&trace_fsmonitor, "refresh fsmonitor");
+
+	if (fsm_mode == FSMONITOR_MODE_IPC) {
+		/* TODO */
+		return;
+	}
+
+	assert(fsm_mode == FSMONITOR_MODE_HOOK);
+
+	hook_version = fsmonitor_hook_version();
+
 	/*
-	 * This could be racy so save the date/time now and query_fsmonitor
+	 * This could be racy so save the date/time now and query_fsmonitor_hook
 	 * should be inclusive to ensure we don't miss potential changes.
 	 */
 	last_update = getnanotime();
@@ -256,13 +271,14 @@  void refresh_fsmonitor(struct index_state *istate)
 		strbuf_addf(&last_update_token, "%"PRIu64"", last_update);
 
 	/*
-	 * If we have a last update token, call query_fsmonitor for the set of
+	 * If we have a last update token, call query_fsmonitor_hook for the set of
 	 * changes since that token, else assume everything is possibly dirty
 	 * and check it all.
 	 */
 	if (istate->fsmonitor_last_update) {
 		if (hook_version == -1 || hook_version == HOOK_INTERFACE_VERSION2) {
-			query_success = !query_fsmonitor(HOOK_INTERFACE_VERSION2,
+			query_success = !query_fsmonitor_hook(
+				r, HOOK_INTERFACE_VERSION2,
 				istate->fsmonitor_last_update, &query_result);
 
 			if (query_success) {
@@ -292,13 +308,17 @@  void refresh_fsmonitor(struct index_state *istate)
 		}
 
 		if (hook_version == HOOK_INTERFACE_VERSION1) {
-			query_success = !query_fsmonitor(HOOK_INTERFACE_VERSION1,
+			query_success = !query_fsmonitor_hook(
+				r, HOOK_INTERFACE_VERSION1,
 				istate->fsmonitor_last_update, &query_result);
 		}
 
-		trace_performance_since(last_update, "fsmonitor process '%s'", core_fsmonitor);
-		trace_printf_key(&trace_fsmonitor, "fsmonitor process '%s' returned %s",
-			core_fsmonitor, query_success ? "success" : "failure");
+		trace_performance_since(last_update, "fsmonitor process '%s'",
+					fsm_settings__get_hook_path(r));
+		trace_printf_key(&trace_fsmonitor,
+				 "fsmonitor process '%s' returned %s",
+				 fsm_settings__get_hook_path(r),
+				 query_success ? "success" : "failure");
 	}
 
 	/*
@@ -434,7 +454,8 @@  void remove_fsmonitor(struct index_state *istate)
 void tweak_fsmonitor(struct index_state *istate)
 {
 	unsigned int i;
-	int fsmonitor_enabled = git_config_get_fsmonitor();
+	struct repository *r = istate->repo ? istate->repo : the_repository;
+	int fsmonitor_enabled = (fsm_settings__get_mode(r) > FSMONITOR_MODE_DISABLED);
 
 	if (istate->fsmonitor_dirty) {
 		if (fsmonitor_enabled) {
@@ -454,16 +475,8 @@  void tweak_fsmonitor(struct index_state *istate)
 		istate->fsmonitor_dirty = NULL;
 	}
 
-	switch (fsmonitor_enabled) {
-	case -1: /* keep: do nothing */
-		break;
-	case 0: /* false */
-		remove_fsmonitor(istate);
-		break;
-	case 1: /* true */
+	if (fsmonitor_enabled)
 		add_fsmonitor(istate);
-		break;
-	default: /* unknown value: do nothing */
-		break;
-	}
+	else
+		remove_fsmonitor(istate);
 }
diff --git a/fsmonitor.h b/fsmonitor.h
index f20d72631d7..f9201411aa7 100644
--- a/fsmonitor.h
+++ b/fsmonitor.h
@@ -3,6 +3,7 @@ 
 
 #include "cache.h"
 #include "dir.h"
+#include "fsmonitor-settings.h"
 
 extern struct trace_key trace_fsmonitor;
 
@@ -57,7 +58,11 @@  int fsmonitor_is_trivial_response(const struct strbuf *query_result);
  */
 static inline int is_fsmonitor_refreshed(const struct index_state *istate)
 {
-	return !core_fsmonitor || istate->fsmonitor_has_run_once;
+	struct repository *r = istate->repo ? istate->repo : the_repository;
+	enum fsmonitor_mode fsm_mode = fsm_settings__get_mode(r);
+
+	return fsm_mode <= FSMONITOR_MODE_DISABLED ||
+		istate->fsmonitor_has_run_once;
 }
 
 /*
@@ -67,7 +72,11 @@  static inline int is_fsmonitor_refreshed(const struct index_state *istate)
  */
 static inline void mark_fsmonitor_valid(struct index_state *istate, struct cache_entry *ce)
 {
-	if (core_fsmonitor && !(ce->ce_flags & CE_FSMONITOR_VALID)) {
+	struct repository *r = istate->repo ? istate->repo : the_repository;
+	enum fsmonitor_mode fsm_mode = fsm_settings__get_mode(r);
+
+	if (fsm_mode > FSMONITOR_MODE_DISABLED &&
+	    !(ce->ce_flags & CE_FSMONITOR_VALID)) {
 		istate->cache_changed = 1;
 		ce->ce_flags |= CE_FSMONITOR_VALID;
 		trace_printf_key(&trace_fsmonitor, "mark_fsmonitor_clean '%s'", ce->name);
@@ -83,7 +92,10 @@  static inline void mark_fsmonitor_valid(struct index_state *istate, struct cache
  */
 static inline void mark_fsmonitor_invalid(struct index_state *istate, struct cache_entry *ce)
 {
-	if (core_fsmonitor) {
+	struct repository *r = istate->repo ? istate->repo : the_repository;
+	enum fsmonitor_mode fsm_mode = fsm_settings__get_mode(r);
+
+	if (fsm_mode > FSMONITOR_MODE_DISABLED) {
 		ce->ce_flags &= ~CE_FSMONITOR_VALID;
 		untracked_cache_invalidate_path(istate, ce->name, 1);
 		trace_printf_key(&trace_fsmonitor, "mark_fsmonitor_invalid '%s'", ce->name);
diff --git a/repo-settings.c b/repo-settings.c
index b93e91a212e..0ca85f54bb8 100644
--- a/repo-settings.c
+++ b/repo-settings.c
@@ -20,6 +20,8 @@  void prepare_repo_settings(struct repository *r)
 	if (r->settings.initialized++)
 		return;
 
+	r->settings.fsmonitor = NULL; /* lazy loaded */
+
 	/* Defaults */
 	r->settings.index_version = -1;
 	r->settings.core_untracked_cache = UNTRACKED_CACHE_KEEP;
diff --git a/repository.h b/repository.h
index a057653981c..89a1873ade7 100644
--- a/repository.h
+++ b/repository.h
@@ -4,6 +4,7 @@ 
 #include "path.h"
 
 struct config_set;
+struct fsmonitor_settings;
 struct git_hash_algo;
 struct index_state;
 struct lock_file;
@@ -34,6 +35,8 @@  struct repo_settings {
 	int command_requires_full_index;
 	int sparse_index;
 
+	struct fsmonitor_settings *fsmonitor; /* lazy loaded */
+
 	int index_version;
 	enum untracked_cache_setting core_untracked_cache;
 
diff --git a/t/README b/t/README
index b92155a822e..6dc4a1d10cf 100644
--- a/t/README
+++ b/t/README
@@ -405,8 +405,8 @@  every 'git commit-graph write', as if the `--changed-paths` option was
 passed in.
 
 GIT_TEST_FSMONITOR=$PWD/t7519/fsmonitor-all exercises the fsmonitor
-code path for utilizing a file system monitor to speed up detecting
-new or changed files.
+code path for utilizing a (hook based) file system monitor to speed up
+detecting new or changed files.
 
 GIT_TEST_INDEX_VERSION=<n> exercises the index read/write code path
 for the index version specified.  Can be set to any valid version