Commit 16a96bdf authored by David Howells's avatar David Howells
Browse files

fscache: Provide a function to resize a cookie 



Provide a function to change the size of the storage attached to a cookie,
to match the size of the file being cached when it's changed by truncate or
fallocate:

	void fscache_resize_cookie(struct fscache_cookie *cookie,
				   loff_t new_size);

This acts synchronously and is expected to run under the inode lock of the
caller.

Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
Reviewed-by: default avatarJeff Layton <jlayton@kernel.org>
cc: linux-cachefs@redhat.com
Link: https://lore.kernel.org/r/163819621839.215744.7895597119803515402.stgit@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/163906922387.143852.16394459879816147793.stgit@warthog.procyon.org.uk/ # v2
Link: https://lore.kernel.org/r/163967128998.1823006.10740669081985775576.stgit@warthog.procyon.org.uk/ # v3
Link: https://lore.kernel.org/r/164021527861.640689.3466382085497236267.stgit@warthog.procyon.org.uk/ # v4
parent 1f67e6d0

fs/fscache/internal.h

+3 −0
Original line number Diff line number Diff line
@@ -122,6 +122,9 @@ extern atomic_t fscache_n_relinquishes; 
extern atomic_t fscache_n_relinquishes_retire;

extern atomic_t fscache_n_relinquishes_dropped;



extern atomic_t fscache_n_resizes;

extern atomic_t fscache_n_resizes_null;



static inline void fscache_stat(atomic_t *stat)

{

	atomic_inc(stat);

fs/fscache/io.c

+25 −0
Original line number Diff line number Diff line
@@ -291,3 +291,28 @@ void __fscache_write_to_cache(struct fscache_cookie *cookie, 
		term_func(term_func_priv, ret, false);

}

EXPORT_SYMBOL(__fscache_write_to_cache);



/*

 * Change the size of a backing object.

 */

void __fscache_resize_cookie(struct fscache_cookie *cookie, loff_t new_size)

{

	struct netfs_cache_resources cres;



	trace_fscache_resize(cookie, new_size);

	if (fscache_begin_operation(&cres, cookie, FSCACHE_WANT_WRITE,

				    fscache_access_io_resize) == 0) {

		fscache_stat(&fscache_n_resizes);

		set_bit(FSCACHE_COOKIE_NEEDS_UPDATE, &cookie->flags);



		/* We cannot defer a resize as we need to do it inside the

		 * netfs's inode lock so that we're serialised with respect to

		 * writes.

		 */

		cookie->volume->cache->ops->resize_cookie(&cres, new_size);

		fscache_end_operation(&cres);

	} else {

		fscache_stat(&fscache_n_resizes_null);

	}

}

EXPORT_SYMBOL(__fscache_resize_cookie);

fs/fscache/stats.c

+7 −2
Original line number Diff line number Diff line
@@ -35,6 +35,9 @@ atomic_t fscache_n_relinquishes; 
atomic_t fscache_n_relinquishes_retire;

atomic_t fscache_n_relinquishes_dropped;



atomic_t fscache_n_resizes;

atomic_t fscache_n_resizes_null;



atomic_t fscache_n_read;

EXPORT_SYMBOL(fscache_n_read);

atomic_t fscache_n_write;
@@ -69,8 +72,10 @@ int fscache_stats_show(struct seq_file *m, void *v) 
	seq_printf(m, "Invals : n=%u\n",

		   atomic_read(&fscache_n_invalidates));



	seq_printf(m, "Updates: n=%u\n",

		   atomic_read(&fscache_n_updates));

	seq_printf(m, "Updates: n=%u rsz=%u rsn=%u\n",

		   atomic_read(&fscache_n_updates),

		   atomic_read(&fscache_n_resizes),

		   atomic_read(&fscache_n_resizes_null));



	seq_printf(m, "Relinqs: n=%u rtr=%u drop=%u\n",

		   atomic_read(&fscache_n_relinquishes),

include/linux/fscache-cache.h

+4 −0
Original line number Diff line number Diff line
@@ -64,6 +64,10 @@ struct fscache_cache_ops { 
	/* Withdraw an object without any cookie access counts held */

	void (*withdraw_cookie)(struct fscache_cookie *cookie);



	/* Change the size of a data object */

	void (*resize_cookie)(struct netfs_cache_resources *cres,

			      loff_t new_size);



	/* Invalidate an object */

	bool (*invalidate_cookie)(struct fscache_cookie *cookie);

include/linux/fscache.h

+18 −0
Original line number Diff line number Diff line
@@ -163,6 +163,7 @@ 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_resize_cookie(struct fscache_cookie *, loff_t);

extern void __fscache_invalidate(struct fscache_cookie *, const void *, loff_t, unsigned int);

extern int __fscache_begin_read_operation(struct netfs_cache_resources *, struct fscache_cookie *);
@@ -366,6 +367,23 @@ void fscache_update_cookie(struct fscache_cookie *cookie, const void *aux_data, 
		__fscache_update_cookie(cookie, aux_data, object_size);

}



/**

 * fscache_resize_cookie - Request that a cache object be resized

 * @cookie: The cookie representing the cache object

 * @new_size: The new size of the object (may be NULL)

 *

 * Request that the size of an object be changed.

 *

 * See Documentation/filesystems/caching/netfs-api.txt for a complete

 * description.

 */

static inline

void fscache_resize_cookie(struct fscache_cookie *cookie, loff_t new_size)

{

	if (fscache_cookie_enabled(cookie))

		__fscache_resize_cookie(cookie, new_size);

}



/**

 * fscache_invalidate - Notify cache that an object needs invalidation

 * @cookie: The cookie representing the cache object