[PATCH v2 1/8] fscache: Generalise the ->begin_read_operation method

From: David Howells
Date: Fri Sep 17 2021 - 11:04:41 EST

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Generalise the ->begin_read_operation() method in the fscache_cache_ops
struct so that it's not read specific by:

(1) changing the name to ->begin_operation();

(2) changing the netfs_read_request struct pointer parameter to be a
netfs_cache_resources struct pointer (it only accesses the cache
resources and an ID for debugging from the read request);

(3) and by changing the fscache_retrieval pointer parameter to be a
fscache_operation pointer (it only access the operation base of the
retrieval).

Also modify the cachefiles implementation so that it stores a pointer to
the fscache_operation rather than fscache_retrieval in the cache resources.

This makes it easier to share code with the write path in future.

Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
Link: https://lore.kernel.org/r/163162768886.438332.9851931782896704604.stgit@xxxxxxxxxxxxxxxxxxxxxx/ # rfc
---

fs/afs/file.c | 2 +-
fs/cachefiles/interface.c | 2 +-
fs/cachefiles/internal.h | 4 ++--
fs/cachefiles/io.c | 28 +++++++++++++---------------
fs/ceph/cache.h | 2 +-
fs/fscache/io.c | 35 +++++++++++++++++++++--------------
include/linux/fscache-cache.h | 6 +++---
include/linux/fscache.h | 15 ++++++++-------
8 files changed, 50 insertions(+), 44 deletions(-)

diff --git a/fs/afs/file.c b/fs/afs/file.c
index db035ae2a134..1563e9871bf6 100644
--- a/fs/afs/file.c
+++ b/fs/afs/file.c
@@ -344,7 +344,7 @@ static int afs_begin_cache_operation(struct netfs_read_request *rreq)
{
struct afs_vnode *vnode = AFS_FS_I(rreq->inode);

- return fscache_begin_read_operation(rreq, afs_vnode_cache(vnode));
+ return fscache_begin_read_operation(&rreq->cache_resources, afs_vnode_cache(vnode));
}

static int afs_check_write_begin(struct file *file, loff_t pos, unsigned len,
diff --git a/fs/cachefiles/interface.c b/fs/cachefiles/interface.c
index da28ac1fa225..8a7755b86c59 100644
--- a/fs/cachefiles/interface.c
+++ b/fs/cachefiles/interface.c
@@ -568,5 +568,5 @@ const struct fscache_cache_ops cachefiles_cache_ops = {
.uncache_page = cachefiles_uncache_page,
.dissociate_pages = cachefiles_dissociate_pages,
.check_consistency = cachefiles_check_consistency,
- .begin_read_operation = cachefiles_begin_read_operation,
+ .begin_operation = cachefiles_begin_operation,
};
diff --git a/fs/cachefiles/internal.h b/fs/cachefiles/internal.h
index 0a511c36dab8..994f90ff12ac 100644
--- a/fs/cachefiles/internal.h
+++ b/fs/cachefiles/internal.h
@@ -198,8 +198,8 @@ extern void cachefiles_uncache_page(struct fscache_object *, struct page *);
/*
* rdwr2.c
*/
-extern int cachefiles_begin_read_operation(struct netfs_read_request *,
- struct fscache_retrieval *);
+extern int cachefiles_begin_operation(struct netfs_cache_resources *,
+ struct fscache_operation *);

/*
* security.c
diff --git a/fs/cachefiles/io.c b/fs/cachefiles/io.c
index fac2e8e7b533..08b3183e0dce 100644
--- a/fs/cachefiles/io.c
+++ b/fs/cachefiles/io.c
@@ -268,7 +268,7 @@ static int cachefiles_write(struct netfs_cache_resources *cres,
static enum netfs_read_source cachefiles_prepare_read(struct netfs_read_subrequest *subreq,
loff_t i_size)
{
- struct fscache_retrieval *op = subreq->rreq->cache_resources.cache_priv;
+ struct fscache_operation *op = subreq->rreq->cache_resources.cache_priv;
struct cachefiles_object *object;
struct cachefiles_cache *cache;
const struct cred *saved_cred;
@@ -277,8 +277,7 @@ static enum netfs_read_source cachefiles_prepare_read(struct netfs_read_subreque

_enter("%zx @%llx/%llx", subreq->len, subreq->start, i_size);

- object = container_of(op->op.object,
- struct cachefiles_object, fscache);
+ object = container_of(op->object, struct cachefiles_object, fscache);
cache = container_of(object->fscache.cache,
struct cachefiles_cache, cache);

@@ -351,7 +350,7 @@ static int cachefiles_prepare_write(struct netfs_cache_resources *cres,
*/
static void cachefiles_end_operation(struct netfs_cache_resources *cres)
{
- struct fscache_retrieval *op = cres->cache_priv;
+ struct fscache_operation *op = cres->cache_priv;
struct file *file = cres->cache_priv2;

_enter("");
@@ -359,8 +358,8 @@ static void cachefiles_end_operation(struct netfs_cache_resources *cres)
if (file)
fput(file);
if (op) {
- fscache_op_complete(&op->op, false);
- fscache_put_retrieval(op);
+ fscache_op_complete(op, false);
+ fscache_put_operation(op);
}

_leave("");
@@ -377,8 +376,8 @@ static const struct netfs_cache_ops cachefiles_netfs_cache_ops = {
/*
* Open the cache file when beginning a cache operation.
*/
-int cachefiles_begin_read_operation(struct netfs_read_request *rreq,
- struct fscache_retrieval *op)
+int cachefiles_begin_operation(struct netfs_cache_resources *cres,
+ struct fscache_operation *op)
{
struct cachefiles_object *object;
struct cachefiles_cache *cache;
@@ -387,8 +386,7 @@ int cachefiles_begin_read_operation(struct netfs_read_request *rreq,

_enter("");

- object = container_of(op->op.object,
- struct cachefiles_object, fscache);
+ object = container_of(op->object, struct cachefiles_object, fscache);
cache = container_of(object->fscache.cache,
struct cachefiles_cache, cache);

@@ -406,11 +404,11 @@ int cachefiles_begin_read_operation(struct netfs_read_request *rreq,
goto error_file;
}

- fscache_get_retrieval(op);
- rreq->cache_resources.cache_priv = op;
- rreq->cache_resources.cache_priv2 = file;
- rreq->cache_resources.ops = &cachefiles_netfs_cache_ops;
- rreq->cache_resources.debug_id = object->fscache.debug_id;
+ atomic_inc(&op->usage);
+ cres->cache_priv = op;
+ cres->cache_priv2 = file;
+ cres->ops = &cachefiles_netfs_cache_ops;
+ cres->debug_id = object->fscache.debug_id;
_leave("");
return 0;

diff --git a/fs/ceph/cache.h b/fs/ceph/cache.h
index 058ea2a04376..b94d3f38fb25 100644
--- a/fs/ceph/cache.h
+++ b/fs/ceph/cache.h
@@ -54,7 +54,7 @@ static inline int ceph_begin_cache_operation(struct netfs_read_request *rreq)
{
struct fscache_cookie *cookie = ceph_fscache_cookie(ceph_inode(rreq->inode));

- return fscache_begin_read_operation(rreq, cookie);
+ return fscache_begin_read_operation(&rreq->cache_resources, cookie);
}
#else

diff --git a/fs/fscache/io.c b/fs/fscache/io.c
index 8ecc1141802f..3745a0631618 100644
--- a/fs/fscache/io.c
+++ b/fs/fscache/io.c
@@ -14,7 +14,7 @@
#include "internal.h"

/*
- * Start a cache read operation.
+ * Start a cache operation.
* - we return:
* -ENOMEM - out of memory, some pages may be being read
* -ERESTARTSYS - interrupted, some pages may be being read
@@ -24,15 +24,16 @@
* the pages
* 0 - dispatched a read on all pages
*/
-int __fscache_begin_read_operation(struct netfs_read_request *rreq,
- struct fscache_cookie *cookie)
+int __fscache_begin_operation(struct netfs_cache_resources *cres,
+ struct fscache_cookie *cookie,
+ bool for_write)
{
- struct fscache_retrieval *op;
+ struct fscache_operation *op;
struct fscache_object *object;
bool wake_cookie = false;
int ret;

- _enter("rr=%08x", rreq->debug_id);
+ _enter("c=%08x", cres->debug_id);

fscache_stat(&fscache_n_retrievals);

@@ -49,10 +50,16 @@ int __fscache_begin_read_operation(struct netfs_read_request *rreq,
if (fscache_wait_for_deferred_lookup(cookie) < 0)
return -ERESTARTSYS;

- op = fscache_alloc_retrieval(cookie, NULL, NULL, NULL);
+ op = kzalloc(sizeof(*op), GFP_KERNEL);
if (!op)
return -ENOMEM;
- trace_fscache_page_op(cookie, NULL, &op->op, fscache_page_op_retr_multi);
+
+ fscache_operation_init(cookie, op, NULL, NULL, NULL);
+ op->flags = FSCACHE_OP_MYTHREAD |
+ (1UL << FSCACHE_OP_WAITING) |
+ (1UL << FSCACHE_OP_UNUSE_COOKIE);
+
+ trace_fscache_page_op(cookie, NULL, op, fscache_page_op_retr_multi);

spin_lock(&cookie->lock);

@@ -64,9 +71,9 @@ int __fscache_begin_read_operation(struct netfs_read_request *rreq,

__fscache_use_cookie(cookie);
atomic_inc(&object->n_reads);
- __set_bit(FSCACHE_OP_DEC_READ_CNT, &op->op.flags);
+ __set_bit(FSCACHE_OP_DEC_READ_CNT, &op->flags);

- if (fscache_submit_op(object, &op->op) < 0)
+ if (fscache_submit_op(object, op) < 0)
goto nobufs_unlock_dec;
spin_unlock(&cookie->lock);

@@ -75,14 +82,14 @@ int __fscache_begin_read_operation(struct netfs_read_request *rreq,
/* we wait for the operation to become active, and then process it
* *here*, in this thread, and not in the thread pool */
ret = fscache_wait_for_operation_activation(
- object, &op->op,
+ object, op,
__fscache_stat(&fscache_n_retrieval_op_waits),
__fscache_stat(&fscache_n_retrievals_object_dead));
if (ret < 0)
goto error;

/* ask the cache to honour the operation */
- ret = object->cache->ops->begin_read_operation(rreq, op);
+ ret = object->cache->ops->begin_operation(cres, op);

error:
if (ret == -ENOMEM)
@@ -96,7 +103,7 @@ int __fscache_begin_read_operation(struct netfs_read_request *rreq,
else
fscache_stat(&fscache_n_retrievals_ok);

- fscache_put_retrieval(op);
+ fscache_put_operation(op);
_leave(" = %d", ret);
return ret;

@@ -105,7 +112,7 @@ int __fscache_begin_read_operation(struct netfs_read_request *rreq,
wake_cookie = __fscache_unuse_cookie(cookie);
nobufs_unlock:
spin_unlock(&cookie->lock);
- fscache_put_retrieval(op);
+ fscache_put_operation(op);
if (wake_cookie)
__fscache_wake_unused_cookie(cookie);
nobufs:
@@ -113,4 +120,4 @@ int __fscache_begin_read_operation(struct netfs_read_request *rreq,
_leave(" = -ENOBUFS");
return -ENOBUFS;
}
-EXPORT_SYMBOL(__fscache_begin_read_operation);
+EXPORT_SYMBOL(__fscache_begin_operation);
diff --git a/include/linux/fscache-cache.h b/include/linux/fscache-cache.h
index 8d39491c5f9f..efa9b6f9fab1 100644
--- a/include/linux/fscache-cache.h
+++ b/include/linux/fscache-cache.h
@@ -304,9 +304,9 @@ struct fscache_cache_ops {
/* dissociate a cache from all the pages it was backing */
void (*dissociate_pages)(struct fscache_cache *cache);

- /* Begin a read operation for the netfs lib */
- int (*begin_read_operation)(struct netfs_read_request *rreq,
- struct fscache_retrieval *op);
+ /* Begin an operation for the netfs lib */
+ int (*begin_operation)(struct netfs_cache_resources *cres,
+ struct fscache_operation *op);
};

extern struct fscache_cookie fscache_fsdef_index;
diff --git a/include/linux/fscache.h b/include/linux/fscache.h
index a4dab5998613..32f65c16328a 100644
--- a/include/linux/fscache.h
+++ b/include/linux/fscache.h
@@ -196,7 +196,8 @@ extern void __fscache_invalidate(struct fscache_cookie *);
extern void __fscache_wait_on_invalidate(struct fscache_cookie *);

#ifdef FSCACHE_USE_NEW_IO_API
-extern int __fscache_begin_read_operation(struct netfs_read_request *, struct fscache_cookie *);
+extern int __fscache_begin_operation(struct netfs_cache_resources *, struct fscache_cookie *,
+ bool);
#else
extern int __fscache_read_or_alloc_page(struct fscache_cookie *,
struct page *,
@@ -511,12 +512,12 @@ int fscache_reserve_space(struct fscache_cookie *cookie, loff_t size)

/**
* fscache_begin_read_operation - Begin a read operation for the netfs lib
- * @rreq: The read request being undertaken
+ * @cres: The cache resources for the read being performed
* @cookie: The cookie representing the cache object
*
- * Begin a read operation on behalf of the netfs helper library. @rreq
- * indicates the read request to which the operation state should be attached;
- * @cookie indicates the cache object that will be accessed.
+ * Begin a read operation on behalf of the netfs helper library. @cres
+ * indicates the cache resources to which the operation state should be
+ * attached; @cookie indicates the cache object that will be accessed.
*
* This is intended to be called from the ->begin_cache_operation() netfs lib
* operation as implemented by the network filesystem.
@@ -527,11 +528,11 @@ int fscache_reserve_space(struct fscache_cookie *cookie, loff_t size)
* * Other error code from the cache, such as -ENOMEM.
*/
static inline
-int fscache_begin_read_operation(struct netfs_read_request *rreq,
+int fscache_begin_read_operation(struct netfs_cache_resources *cres,
struct fscache_cookie *cookie)
{
if (fscache_cookie_valid(cookie) && fscache_cookie_enabled(cookie))
- return __fscache_begin_read_operation(rreq, cookie);
+ return __fscache_begin_operation(cres, cookie, false);
return -ENOBUFS;
}

Next message: Marco Elver: "Re: [PATCH 2/3] kfence: limit currently covered allocations when pool nearly full"
Previous message: Pavel Skripkin: "Re: [PATCH v7 19/19] staging: r8188eu: remove shared buffer for usb requests"
In reply to: David Howells: "[RFC PATCH v2 0/8] fscache: Replace and remove old I/O API v2"
Next in thread: David Howells: "[PATCH v2 2/8] fscache: Implement a fallback I/O interface to replace the old API"
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