[PATCH 19/64] fscache: Implement cookie invalidation

From: David Howells
Date: Mon Nov 29 2021 - 09:29:37 EST

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Add a function to invalidate the cache behind a cookie:

void fscache_invalidate(struct fscache_cookie *cookie,
const void *aux_data,
loff_t size,
unsigned int flags)

This causes any cached data for the specified cookie to be discarded. If
the cookie is marked as being in use, a new cache object will be created if
possible and future I/O will use that instead. In-flight I/O should be
abandoned (writes) or reconsidered (reads). Each time it is called
cookie->inval_counter is incremented and this can be used to detect
invalidation at the end of an I/O operation.

The coherency data attached to the cookie can be updated and the cookie
size should be reset. One flag is available, FSCACHE_INVAL_DIO_WRITE,
which should be used to indicate invalidation due to a DIO write on a
file. This will temporarily disable caching for this cookie.

Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
cc: linux-cachefs@xxxxxxxxxx
---

fs/fscache/cookie.c | 87 ++++++++++++++++++++++++++++++++++++++++
fs/fscache/internal.h | 2 +
fs/fscache/stats.c | 5 ++
include/linux/fscache-cache.h | 4 ++
include/linux/fscache.h | 31 ++++++++++++++
include/linux/netfs.h | 1
include/trace/events/fscache.h | 25 +++++++++++
7 files changed, 154 insertions(+), 1 deletion(-)

diff --git a/fs/fscache/cookie.c b/fs/fscache/cookie.c
index f056f834639b..7919d7f5747b 100644
--- a/fs/fscache/cookie.c
+++ b/fs/fscache/cookie.c
@@ -19,6 +19,7 @@ static void fscache_cookie_lru_timed_out(struct timer_list *timer);
static void fscache_cookie_lru_worker(struct work_struct *work);
static void fscache_cookie_worker(struct work_struct *work);
static void fscache_unhash_cookie(struct fscache_cookie *cookie);
+static void fscache_perform_invalidation(struct fscache_cookie *cookie);

#define fscache_cookie_hash_shift 15
static struct hlist_bl_head fscache_cookie_hash[1 << fscache_cookie_hash_shift];
@@ -28,7 +29,7 @@ static LIST_HEAD(fscache_cookie_lru);
static DEFINE_SPINLOCK(fscache_cookie_lru_lock);
DEFINE_TIMER(fscache_cookie_lru_timer, fscache_cookie_lru_timed_out);
static DECLARE_WORK(fscache_cookie_lru_work, fscache_cookie_lru_worker);
-static const char fscache_cookie_states[FSCACHE_COOKIE_STATE__NR] = "-LCAFUWRD";
+static const char fscache_cookie_states[FSCACHE_COOKIE_STATE__NR] = "-LCAIFUWRD";
unsigned int fscache_lru_cookie_timeout = 10 * HZ;

void fscache_print_cookie(struct fscache_cookie *cookie, char prefix)
@@ -228,6 +229,19 @@ void fscache_cookie_lookup_negative(struct fscache_cookie *cookie)
}
EXPORT_SYMBOL(fscache_cookie_lookup_negative);

+/**
+ * fscache_resume_after_invalidation - Allow I/O to resume after invalidation
+ * @cookie: The cookie that was invalidated
+ *
+ * Tell fscache that invalidation is sufficiently complete that I/O can be
+ * allowed again.
+ */
+void fscache_resume_after_invalidation(struct fscache_cookie *cookie)
+{
+ fscache_set_cookie_state(cookie, FSCACHE_COOKIE_STATE_ACTIVE);
+}
+EXPORT_SYMBOL(fscache_resume_after_invalidation);
+
/**
* fscache_caching_failed - Report that a failure stopped caching on a cookie
* @cookie: The cookie that was affected
@@ -558,6 +572,7 @@ void __fscache_use_cookie(struct fscache_cookie *cookie, bool will_modify)
set_bit(FSCACHE_COOKIE_LOCAL_WRITE, &cookie->flags);
break;
case FSCACHE_COOKIE_STATE_ACTIVE:
+ case FSCACHE_COOKIE_STATE_INVALIDATING:
if (will_modify &&
!test_and_set_bit(FSCACHE_COOKIE_LOCAL_WRITE, &cookie->flags)) {
set_bit(FSCACHE_COOKIE_DO_PREP_TO_WRITE, &cookie->flags);
@@ -663,6 +678,11 @@ static void fscache_cookie_state_machine(struct fscache_cookie *cookie)
fscache_perform_lookup(cookie);
goto again;

+ case FSCACHE_COOKIE_STATE_INVALIDATING:
+ spin_unlock(&cookie->lock);
+ fscache_perform_invalidation(cookie);
+ goto again;
+
case FSCACHE_COOKIE_STATE_ACTIVE:
if (test_and_clear_bit(FSCACHE_COOKIE_DO_PREP_TO_WRITE, &cookie->flags)) {
spin_unlock(&cookie->lock);
@@ -939,6 +959,71 @@ struct fscache_cookie *fscache_get_cookie(struct fscache_cookie *cookie,
}
EXPORT_SYMBOL(fscache_get_cookie);

+/*
+ * Ask the cache to effect invalidation of a cookie.
+ */
+static void fscache_perform_invalidation(struct fscache_cookie *cookie)
+{
+ if (!cookie->volume->cache->ops->invalidate_cookie(cookie))
+ fscache_caching_failed(cookie);
+ fscache_end_cookie_access(cookie, fscache_access_invalidate_cookie_end);
+}
+
+/*
+ * Invalidate an object.
+ */
+void __fscache_invalidate(struct fscache_cookie *cookie,
+ const void *aux_data, loff_t new_size,
+ unsigned int flags)
+{
+ bool is_caching;
+
+ _enter("c=%x", cookie->debug_id);
+
+ fscache_stat(&fscache_n_invalidates);
+
+ if (WARN(test_bit(FSCACHE_COOKIE_RELINQUISHED, &cookie->flags),
+ "Trying to invalidate relinquished cookie\n"))
+ return;
+
+ if ((flags & FSCACHE_INVAL_DIO_WRITE) &&
+ test_and_set_bit(FSCACHE_COOKIE_DISABLED, &cookie->flags))
+ return;
+
+ spin_lock(&cookie->lock);
+ set_bit(FSCACHE_COOKIE_NO_DATA_TO_READ, &cookie->flags);
+ fscache_update_aux(cookie, aux_data, &new_size);
+ cookie->inval_counter++;
+ trace_fscache_invalidate(cookie, new_size);
+
+ switch (cookie->state) {
+ case FSCACHE_COOKIE_STATE_INVALIDATING: /* is_still_valid will catch it */
+ default:
+ spin_unlock(&cookie->lock);
+ _leave(" [no %u]", cookie->state);
+ return;
+
+ case FSCACHE_COOKIE_STATE_LOOKING_UP:
+ case FSCACHE_COOKIE_STATE_CREATING:
+ spin_unlock(&cookie->lock);
+ _leave(" [look %x]", cookie->inval_counter);
+ return;
+
+ case FSCACHE_COOKIE_STATE_ACTIVE:
+ __fscache_set_cookie_state(cookie, FSCACHE_COOKIE_STATE_INVALIDATING);
+ is_caching = fscache_begin_cookie_access(
+ cookie, fscache_access_invalidate_cookie);
+ spin_unlock(&cookie->lock);
+ wake_up_cookie_state(cookie);
+
+ if (is_caching)
+ fscache_queue_cookie(cookie, fscache_cookie_get_inval_work);
+ _leave(" [inv]");
+ return;
+ }
+}
+EXPORT_SYMBOL(__fscache_invalidate);
+
/*
* Generate a list of extant cookies in /proc/fs/fscache/cookies
*/
diff --git a/fs/fscache/internal.h b/fs/fscache/internal.h
index 9af8de906bf0..e4f3a1a993f6 100644
--- a/fs/fscache/internal.h
+++ b/fs/fscache/internal.h
@@ -105,6 +105,8 @@ extern atomic_t fscache_n_acquires;
extern atomic_t fscache_n_acquires_ok;
extern atomic_t fscache_n_acquires_oom;

+extern atomic_t fscache_n_invalidates;
+
extern atomic_t fscache_n_relinquishes;
extern atomic_t fscache_n_relinquishes_retire;
extern atomic_t fscache_n_relinquishes_dropped;
diff --git a/fs/fscache/stats.c b/fs/fscache/stats.c
index 5aa4bd9fe207..cdbb672a274f 100644
--- a/fs/fscache/stats.c
+++ b/fs/fscache/stats.c
@@ -26,6 +26,8 @@ atomic_t fscache_n_acquires;
atomic_t fscache_n_acquires_ok;
atomic_t fscache_n_acquires_oom;

+atomic_t fscache_n_invalidates;
+
atomic_t fscache_n_updates;
EXPORT_SYMBOL(fscache_n_updates);

@@ -59,6 +61,9 @@ int fscache_stats_show(struct seq_file *m, void *v)
timer_pending(&fscache_cookie_lru_timer) ?
fscache_cookie_lru_timer.expires - jiffies : 0);

+ seq_printf(m, "Invals : n=%u\n",
+ atomic_read(&fscache_n_invalidates));
+
seq_printf(m, "Updates: n=%u\n",
atomic_read(&fscache_n_updates));

diff --git a/include/linux/fscache-cache.h b/include/linux/fscache-cache.h
index ae6a75976450..1ad56bfd9d72 100644
--- a/include/linux/fscache-cache.h
+++ b/include/linux/fscache-cache.h
@@ -64,6 +64,9 @@ struct fscache_cache_ops {
/* Withdraw an object without any cookie access counts held */
void (*withdraw_cookie)(struct fscache_cookie *cookie);

+ /* Invalidate an object */
+ bool (*invalidate_cookie)(struct fscache_cookie *cookie);
+
/* Prepare to write to a live cache object */
void (*prepare_to_write)(struct fscache_cookie *cookie);
};
@@ -96,6 +99,7 @@ extern void fscache_put_cookie(struct fscache_cookie *cookie,
extern void fscache_end_cookie_access(struct fscache_cookie *cookie,
enum fscache_access_trace why);
extern void fscache_cookie_lookup_negative(struct fscache_cookie *cookie);
+extern void fscache_resume_after_invalidation(struct fscache_cookie *cookie);
extern void fscache_caching_failed(struct fscache_cookie *cookie);

/**
diff --git a/include/linux/fscache.h b/include/linux/fscache.h
index c5b7eeb76835..cfbace3bdc88 100644
--- a/include/linux/fscache.h
+++ b/include/linux/fscache.h
@@ -39,6 +39,8 @@ struct fscache_cookie;
#define FSCACHE_ADV_WRITE_CACHE 0x00 /* Do cache if written to locally */
#define FSCACHE_ADV_WRITE_NOCACHE 0x02 /* Don't cache if written to locally */

+#define FSCACHE_INVAL_DIO_WRITE 0x01 /* Invalidate due to DIO write */
+
/*
* Data object state.
*/
@@ -47,6 +49,7 @@ enum fscache_cookie_state {
FSCACHE_COOKIE_STATE_LOOKING_UP, /* The cache object is being looked up */
FSCACHE_COOKIE_STATE_CREATING, /* The cache object is being created */
FSCACHE_COOKIE_STATE_ACTIVE, /* The cache is active, readable and writable */
+ FSCACHE_COOKIE_STATE_INVALIDATING, /* The cache is being invalidated */
FSCACHE_COOKIE_STATE_FAILED, /* The cache failed, withdraw to clear */
FSCACHE_COOKIE_STATE_LRU_DISCARDING, /* The cookie is being discarded by the LRU */
FSCACHE_COOKIE_STATE_WITHDRAWING, /* The cookie is being withdrawn */
@@ -152,6 +155,7 @@ extern struct fscache_cookie *__fscache_acquire_cookie(
extern void __fscache_use_cookie(struct fscache_cookie *, bool);
extern void __fscache_unuse_cookie(struct fscache_cookie *, const void *, const loff_t *);
extern void __fscache_relinquish_cookie(struct fscache_cookie *, bool);
+extern void __fscache_invalidate(struct fscache_cookie *, const void *, loff_t, unsigned int);

/**
* fscache_acquire_volume - Register a volume as desiring caching services
@@ -319,4 +323,31 @@ void __fscache_update_cookie(struct fscache_cookie *cookie, const void *aux_data
set_bit(FSCACHE_COOKIE_NEEDS_UPDATE, &cookie->flags);
}

+/**
+ * fscache_invalidate - Notify cache that an object needs invalidation
+ * @cookie: The cookie representing the cache object
+ * @aux_data: The updated auxiliary data for the cookie (may be NULL)
+ * @size: The revised size of the object.
+ * @flags: Invalidation flags (FSCACHE_INVAL_*)
+ *
+ * Notify the cache that an object is needs to be invalidated and that it
+ * should abort any retrievals or stores it is doing on the cache. This
+ * increments inval_counter on the cookie which can be used by the caller to
+ * reconsider I/O requests as they complete.
+ *
+ * If @flags has FSCACHE_INVAL_DIO_WRITE set, this indicates that this is due
+ * to a direct I/O write and will cause caching to be disabled on this cookie
+ * until it is completely unused.
+ *
+ * See Documentation/filesystems/caching/netfs-api.rst for a complete
+ * description.
+ */
+static inline
+void fscache_invalidate(struct fscache_cookie *cookie,
+ const void *aux_data, loff_t size, unsigned int flags)
+{
+ if (fscache_cookie_enabled(cookie))
+ __fscache_invalidate(cookie, aux_data, size, flags);
+}
+
#endif /* _LINUX_FSCACHE_H */
diff --git a/include/linux/netfs.h b/include/linux/netfs.h
index 1ea22fc48818..5a46fde65759 100644
--- a/include/linux/netfs.h
+++ b/include/linux/netfs.h
@@ -124,6 +124,7 @@ struct netfs_cache_resources {
void *cache_priv;
void *cache_priv2;
unsigned int debug_id; /* Cookie debug ID */
+ unsigned int inval_counter; /* object->inval_counter at begin_op */
};

/*
diff --git a/include/trace/events/fscache.h b/include/trace/events/fscache.h
index 17654fa657a6..5f88479fb06a 100644
--- a/include/trace/events/fscache.h
+++ b/include/trace/events/fscache.h
@@ -51,6 +51,7 @@ enum fscache_cookie_trace {
fscache_cookie_discard,
fscache_cookie_get_end_access,
fscache_cookie_get_hash_collision,
+ fscache_cookie_get_inval_work,
fscache_cookie_get_lru,
fscache_cookie_get_use_work,
fscache_cookie_new_acquire,
@@ -73,6 +74,8 @@ enum fscache_access_trace {
fscache_access_acquire_volume_end,
fscache_access_cache_pin,
fscache_access_cache_unpin,
+ fscache_access_invalidate_cookie,
+ fscache_access_invalidate_cookie_end,
fscache_access_lookup_cookie,
fscache_access_lookup_cookie_end,
fscache_access_lookup_cookie_end_failed,
@@ -116,6 +119,7 @@ enum fscache_access_trace {
EM(fscache_cookie_discard, "DISCARD ") \
EM(fscache_cookie_get_hash_collision, "GET hcoll") \
EM(fscache_cookie_get_end_access, "GQ endac") \
+ EM(fscache_cookie_get_inval_work, "GQ inval") \
EM(fscache_cookie_get_lru, "GET lru ") \
EM(fscache_cookie_get_use_work, "GQ use ") \
EM(fscache_cookie_new_acquire, "NEW acq ") \
@@ -137,6 +141,8 @@ enum fscache_access_trace {
EM(fscache_access_acquire_volume_end, "END acq_vol") \
EM(fscache_access_cache_pin, "PIN cache ") \
EM(fscache_access_cache_unpin, "UNPIN cache ") \
+ EM(fscache_access_invalidate_cookie, "BEGIN inval ") \
+ EM(fscache_access_invalidate_cookie_end,"END inval ") \
EM(fscache_access_lookup_cookie, "BEGIN lookup ") \
EM(fscache_access_lookup_cookie_end, "END lookup ") \
EM(fscache_access_lookup_cookie_end_failed,"END lookupf") \
@@ -386,6 +392,25 @@ TRACE_EVENT(fscache_relinquish,
__entry->n_active, __entry->flags, __entry->retire)
);

+TRACE_EVENT(fscache_invalidate,
+ TP_PROTO(struct fscache_cookie *cookie, loff_t new_size),
+
+ TP_ARGS(cookie, new_size),
+
+ TP_STRUCT__entry(
+ __field(unsigned int, cookie )
+ __field(loff_t, new_size )
+ ),
+
+ TP_fast_assign(
+ __entry->cookie = cookie->debug_id;
+ __entry->new_size = new_size;
+ ),
+
+ TP_printk("c=%08x sz=%llx",
+ __entry->cookie, __entry->new_size)
+ );
+
#endif /* _TRACE_FSCACHE_H */

/* This part must be outside protection */

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Previous message: David Howells: "[PATCH 18/64] fscache: Implement cookie user counting and resource pinning"
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