Commit 32e15003 authored by David Howells's avatar David Howells
Browse files

fscache, cachefiles: Store the volume coherency data 



Store the volume coherency data in an xattr and check it when we rebind the
volume.  If it doesn't match the cache volume is moved to the graveyard and
rebuilt anew.

Changes
=======
ver #4:
 - Remove a couple of debugging prints.

Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
Reviewed-by: default avatarJeff Layton <jlayton@kernel.org>
Link: https://lore.kernel.org/r/163967164397.1823006.2950539849831291830.stgit@warthog.procyon.org.uk/ # v3
Link: https://lore.kernel.org/r/164021563138.640689.15851092065380543119.stgit@warthog.procyon.org.uk/ # v4
parent 047487c9

fs/cachefiles/internal.h

+2 −0
Original line number Diff line number Diff line
@@ -270,6 +270,8 @@ extern int cachefiles_remove_object_xattr(struct cachefiles_cache *cache, 
					  struct cachefiles_object *object,

					  struct dentry *dentry);

extern void cachefiles_prepare_to_write(struct fscache_cookie *cookie);

extern bool cachefiles_set_volume_xattr(struct cachefiles_volume *volume);

extern int cachefiles_check_volume_xattr(struct cachefiles_volume *volume);



/*

 * Error handling

fs/cachefiles/volume.c

+23 −2
Original line number Diff line number Diff line
@@ -22,7 +22,8 @@ void cachefiles_acquire_volume(struct fscache_volume *vcookie) 
	struct dentry *vdentry, *fan;

	size_t len;

	char *name;

	int n_accesses, i;

	bool is_new = false;

	int ret, n_accesses, i;



	_enter("");
@@ -43,11 +44,29 @@ void cachefiles_acquire_volume(struct fscache_volume *vcookie) 
	memcpy(name + 1, vcookie->key + 1, len);

	name[len + 1] = 0;



	vdentry = cachefiles_get_directory(cache, cache->store, name, NULL);

retry:

	vdentry = cachefiles_get_directory(cache, cache->store, name, &is_new);

	if (IS_ERR(vdentry))

		goto error_name;

	volume->dentry = vdentry;



	if (is_new) {

		if (!cachefiles_set_volume_xattr(volume))

			goto error_dir;

	} else {

		ret = cachefiles_check_volume_xattr(volume);

		if (ret < 0) {

			if (ret != -ESTALE)

				goto error_dir;

			inode_lock_nested(d_inode(cache->store), I_MUTEX_PARENT);

			cachefiles_bury_object(cache, NULL, cache->store, vdentry,

					       FSCACHE_VOLUME_IS_WEIRD);

			cachefiles_put_directory(volume->dentry);

			cond_resched();

			goto retry;

		}

	}

	

	for (i = 0; i < 256; i++) {

		sprintf(name, "@%02x", i);

		fan = cachefiles_get_directory(cache, vdentry, name, NULL);
@@ -74,6 +93,7 @@ void cachefiles_acquire_volume(struct fscache_volume *vcookie) 
error_fan:

	for (i = 0; i < 256; i++)

		cachefiles_put_directory(volume->fanout[i]);

error_dir:

	cachefiles_put_directory(volume->dentry);

error_name:

	kfree(name);
@@ -114,5 +134,6 @@ void cachefiles_free_volume(struct fscache_volume *vcookie) 
void cachefiles_withdraw_volume(struct cachefiles_volume *volume)

{

	fscache_withdraw_volume(volume->vcookie);

	cachefiles_set_volume_xattr(volume);

	__cachefiles_free_volume(volume);

}

fs/cachefiles/xattr.c

+78 −0
Original line number Diff line number Diff line
@@ -179,3 +179,81 @@ void cachefiles_prepare_to_write(struct fscache_cookie *cookie) 
		cachefiles_end_secure(cache, saved_cred);

	}

}



/*

 * Set the state xattr on a volume directory.

 */

bool cachefiles_set_volume_xattr(struct cachefiles_volume *volume)

{

	unsigned int len = volume->vcookie->coherency_len;

	const void *p = volume->vcookie->coherency;

	struct dentry *dentry = volume->dentry;

	int ret;



	_enter("%x,#%d", volume->vcookie->debug_id, len);



	ret = cachefiles_inject_write_error();

	if (ret == 0)

		ret = vfs_setxattr(&init_user_ns, dentry, cachefiles_xattr_cache,

				   p, len, 0);

	if (ret < 0) {

		trace_cachefiles_vfs_error(NULL, d_inode(dentry), ret,

					   cachefiles_trace_setxattr_error);

		trace_cachefiles_vol_coherency(volume, d_inode(dentry)->i_ino,

					       cachefiles_coherency_vol_set_fail);

		if (ret != -ENOMEM)

			cachefiles_io_error(

				volume->cache, "Failed to set xattr with error %d", ret);

	} else {

		trace_cachefiles_vol_coherency(volume, d_inode(dentry)->i_ino,

					       cachefiles_coherency_vol_set_ok);

	}



	_leave(" = %d", ret);

	return ret == 0;

}



/*

 * Check the consistency between the backing cache and the volume cookie.

 */

int cachefiles_check_volume_xattr(struct cachefiles_volume *volume)

{

	struct cachefiles_xattr *buf;

	struct dentry *dentry = volume->dentry;

	unsigned int len = volume->vcookie->coherency_len;

	const void *p = volume->vcookie->coherency;

	enum cachefiles_coherency_trace why;

	ssize_t xlen;

	int ret = -ESTALE;



	_enter("");



	buf = kmalloc(len, GFP_KERNEL);

	if (!buf)

		return -ENOMEM;



	xlen = cachefiles_inject_read_error();

	if (xlen == 0)

		xlen = vfs_getxattr(&init_user_ns, dentry, cachefiles_xattr_cache, buf, len);

	if (xlen != len) {

		if (xlen < 0) {

			trace_cachefiles_vfs_error(NULL, d_inode(dentry), xlen,

						   cachefiles_trace_getxattr_error);

			if (xlen == -EIO)

				cachefiles_io_error(

					volume->cache,

					"Failed to read xattr with error %zd", xlen);

		}

		why = cachefiles_coherency_vol_check_xattr;

	} else if (memcmp(buf->data, p, len) != 0) {

		why = cachefiles_coherency_vol_check_cmp;

	} else {

		why = cachefiles_coherency_vol_check_ok;

		ret = 0;

	}



	trace_cachefiles_vol_coherency(volume, d_inode(dentry)->i_ino, why);

	kfree(buf);

	_leave(" = %d", ret);

	return ret;

}

fs/fscache/volume.c

+12 −2
Original line number Diff line number Diff line
@@ -205,15 +205,22 @@ static struct fscache_volume *fscache_alloc_volume(const char *volume_key, 
	size_t klen, hlen;

	char *key;



	if (!coherency_data)

		coherency_len = 0;



	cache = fscache_lookup_cache(cache_name, false);

	if (IS_ERR(cache))

		return NULL;



	volume = kzalloc(sizeof(*volume), GFP_KERNEL);

	volume = kzalloc(struct_size(volume, coherency, coherency_len),

			 GFP_KERNEL);

	if (!volume)

		goto err_cache;



	volume->cache = cache;

	volume->coherency_len = coherency_len;

	if (coherency_data)

		memcpy(volume->coherency, coherency_data, coherency_len);

	INIT_LIST_HEAD(&volume->proc_link);

	INIT_WORK(&volume->work, fscache_create_volume_work);

	refcount_set(&volume->ref, 1);
@@ -421,8 +428,11 @@ void __fscache_relinquish_volume(struct fscache_volume *volume, 
	if (WARN_ON(test_and_set_bit(FSCACHE_VOLUME_RELINQUISHED, &volume->flags)))

		return;



	if (invalidate)

	if (invalidate) {

		set_bit(FSCACHE_VOLUME_INVALIDATE, &volume->flags);

	} else if (coherency_data) {

		memcpy(volume->coherency, coherency_data, volume->coherency_len);

	}



	fscache_put_volume(volume, fscache_volume_put_relinquish);

}

include/linux/fscache.h

+2 −0
Original line number Diff line number Diff line
@@ -87,6 +87,8 @@ struct fscache_volume { 
#define FSCACHE_VOLUME_COLLIDED_WITH	2	/* Volume was collided with */

#define FSCACHE_VOLUME_ACQUIRE_PENDING	3	/* Volume is waiting to complete acquisition */

#define FSCACHE_VOLUME_CREATING		4	/* Volume is being created on disk */

	u8				coherency_len;	/* Length of the coherency data */

	u8				coherency[];	/* Coherency data */

};



/*