Commit a235d7d9 authored by Dan Williams's avatar Dan Williams Committed by Dave Jiang
Browse files

cxl/region: Split commit_store() into __commit() and queue_reset() helpers 



The complexity of dropping the lock is removed in favor of splitting commit
operations to a helper, and leaving all the complexities of "decommit" for
commit_store() to coordinate the different locking contexts.

The CPU cache-invalidation in the decommit path is solely handled now by
cxl_region_decode_reset(). Previously the CPU caches were being needlessly
flushed twice in the decommit path where the first flush had no guarantee
that the memory would not be immediately re-dirtied.

Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Jonathan Cameron <jonathan.cameron@huawei.com>
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: Alison Schofield <alison.schofield@intel.com>
Cc: Vishal Verma <vishal.l.verma@intel.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Acked-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarDave Jiang <dave.jiang@intel.com>
Reviewed-by: default avatarJonathan Cameron <jonathan.cameron@huawei.com>
Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
Reviewed-by: default avatarFabio M. De Francesco <fabio.m.de.francesco@linux.intel.com>
Link: https://patch.msgid.link/20250711234932.671292-6-dan.j.williams@intel.com


Signed-off-by: default avatarDave Jiang <dave.jiang@intel.com>
parent 55a89d9c

drivers/cxl/core/region.c

+70 −29
Original line number Diff line number Diff line
@@ -349,30 +349,42 @@ static int cxl_region_decode_commit(struct cxl_region *cxlr) 
	return rc;

}



static ssize_t commit_store(struct device *dev, struct device_attribute *attr,

			    const char *buf, size_t len)

static int queue_reset(struct cxl_region *cxlr)

{

	struct cxl_region *cxlr = to_cxl_region(dev);

	struct cxl_region_params *p = &cxlr->params;

	bool commit;

	ssize_t rc;

	int rc;



	rc = kstrtobool(buf, &commit);

	rc = down_write_killable(&cxl_region_rwsem);

	if (rc)

		return rc;



	/* Already in the requested state? */

	if (p->state < CXL_CONFIG_COMMIT)

		goto out;



	p->state = CXL_CONFIG_RESET_PENDING;



out:

	up_write(&cxl_region_rwsem);



	return rc;

}



static int __commit(struct cxl_region *cxlr)

{

	struct cxl_region_params *p = &cxlr->params;

	int rc;



	rc = down_write_killable(&cxl_region_rwsem);

	if (rc)

		return rc;



	/* Already in the requested state? */

	if (commit && p->state >= CXL_CONFIG_COMMIT)

		goto out;

	if (!commit && p->state < CXL_CONFIG_COMMIT)

	if (p->state >= CXL_CONFIG_COMMIT)

		goto out;



	/* Not ready to commit? */

	if (commit && p->state < CXL_CONFIG_ACTIVE) {

	if (p->state < CXL_CONFIG_ACTIVE) {

		rc = -ENXIO;

		goto out;

	}
@@ -385,31 +397,60 @@ static ssize_t commit_store(struct device *dev, struct device_attribute *attr, 
	if (rc)

		goto out;



	if (commit) {

	rc = cxl_region_decode_commit(cxlr);

	if (rc == 0)

		p->state = CXL_CONFIG_COMMIT;

	} else {

		p->state = CXL_CONFIG_RESET_PENDING;



out:

	up_write(&cxl_region_rwsem);



	return rc;

}



static ssize_t commit_store(struct device *dev, struct device_attribute *attr,

			    const char *buf, size_t len)

{

	struct cxl_region *cxlr = to_cxl_region(dev);

	struct cxl_region_params *p = &cxlr->params;

	bool commit;

	ssize_t rc;



	rc = kstrtobool(buf, &commit);

	if (rc)

		return rc;



	if (commit) {

		rc = __commit(cxlr);

		if (rc)

			return rc;

		return len;

	}



	rc = queue_reset(cxlr);

	if (rc)

		return rc;



	/*

	 * Unmap the region and depend the reset-pending state to ensure

	 * it does not go active again until post reset

	 */

	device_release_driver(&cxlr->dev);

		down_write(&cxl_region_rwsem);



	/*

		 * The lock was dropped, so need to revalidate that the reset is

		 * still pending.

	 * With the reset pending take cxl_region_rwsem unconditionally

	 * to ensure the reset gets handled before returning.

	 */

	guard(rwsem_write)(&cxl_region_rwsem);



	/*

	 * Revalidate that the reset is still pending in case another

	 * thread already handled this reset.

	 */

	if (p->state == CXL_CONFIG_RESET_PENDING) {

		cxl_region_decode_reset(cxlr, p->interleave_ways);

		p->state = CXL_CONFIG_ACTIVE;

	}

	}



out:

	up_write(&cxl_region_rwsem);



	if (rc)

		return rc;

	return len;

}