Re: [PATCH v2 13/38] cxlflash: Support adapter file descriptors for OCXL

On Mar 22, 2018, at 12:12 PM, Frederic Barrat =

[off-list ref] wrote:

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Le 26/02/2018 =C3=A0 23:21, Uma Krishnan a =C3=A9crit :

quoted

Allocate a file descriptor for an adapter context when requested. In =

order

quoted

to allocate inodes for the file descriptors, a pseudo filesystem is =

created

quoted

and used.
Signed-off-by: Uma Krishnan <redacted>
Acked-by: Matthew R. Ochs <redacted>
---

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We've touched the subject before, and I don't have a magic solution, =

but it feels like something could be shared here with cxl, or maybe even =
other drivers?

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Yes, perhaps we could look at refactoring in a future series.

I only took a quick read of the inode allocator.
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 Fred
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quoted

 drivers/scsi/cxlflash/ocxl_hw.c | 200 =

++++++++++++++++++++++++++++++++++++++++

quoted

 drivers/scsi/cxlflash/ocxl_hw.h |   1 +
 2 files changed, 201 insertions(+)

diff --git a/drivers/scsi/cxlflash/ocxl_hw.c =

b/drivers/scsi/cxlflash/ocxl_hw.c

quoted

index 6472210..59e9003 100644

--- a/drivers/scsi/cxlflash/ocxl_hw.c
+++ b/drivers/scsi/cxlflash/ocxl_hw.c

@@ -12,13 +12,144 @@
  * 2 of the License, or (at your option) any later version.
  */
+#include <linux/file.h>
 #include <linux/idr.h>
+#include <linux/module.h>
+#include <linux/mount.h>
 #include <misc/ocxl.h>
 #include "backend.h"
 #include "ocxl_hw.h"
+/*
+ * Pseudo-filesystem to allocate inodes.
+ */
+
+#define OCXLFLASH_FS_MAGIC      0x1697698f
+
+static int ocxlflash_fs_cnt;
+static struct vfsmount *ocxlflash_vfs_mount;
+
+static const struct dentry_operations ocxlflash_fs_dops =3D {
+	.d_dname	=3D simple_dname,
+};
+
+/*
+ * ocxlflash_fs_mount() - mount the pseudo-filesystem
+ * @fs_type:	File system type.
+ * @flags:	Flags for the filesystem.
+ * @dev_name:	Device name associated with the filesystem.
+ * @data:	Data pointer.
+ *
+ * Return: pointer to the directory entry structure
+ */
+static struct dentry *ocxlflash_fs_mount(struct file_system_type =

*fs_type,

quoted

+					 int flags, const char =

*dev_name,

quoted

+					 void *data)
+{
+	return mount_pseudo(fs_type, "ocxlflash:", NULL, =

&ocxlflash_fs_dops,

quoted

+			    OCXLFLASH_FS_MAGIC);
+}
+
+static struct file_system_type ocxlflash_fs_type =3D {
+	.name		=3D "ocxlflash",
+	.owner		=3D THIS_MODULE,
+	.mount		=3D ocxlflash_fs_mount,
+	.kill_sb	=3D kill_anon_super,
+};
+
+/*
+ * ocxlflash_release_mapping() - release the memory mapping
+ * @ctx:	Context whose mapping is to be released.
+ */
+static void ocxlflash_release_mapping(struct ocxlflash_context *ctx)
+{
+	if (ctx->mapping)
+		simple_release_fs(&ocxlflash_vfs_mount, =

&ocxlflash_fs_cnt);

quoted

+	ctx->mapping =3D NULL;
+}
+
+/*
+ * ocxlflash_getfile() - allocate pseudo filesystem, inode, and the =

file

quoted

+ * @dev:	Generic device of the host.
+ * @name:	Name of the pseudo filesystem.
+ * @fops:	File operations.
+ * @priv:	Private data.
+ * @flags:	Flags for the file.
+ *
+ * Return: pointer to the file on success, ERR_PTR on failure
+ */
+static struct file *ocxlflash_getfile(struct device *dev, const char =

*name,

quoted

+				      const struct file_operations =

*fops,

quoted

+				      void *priv, int flags)
+{
+	struct qstr this;
+	struct path path;
+	struct file *file;
+	struct inode *inode =3D NULL;
+	int rc;
+
+	if (fops->owner && !try_module_get(fops->owner)) {
+		dev_err(dev, "%s: Owner does not exist\n", __func__);
+		rc =3D -ENOENT;
+		goto err1;
+	}
+
+	rc =3D simple_pin_fs(&ocxlflash_fs_type, &ocxlflash_vfs_mount,
+			   &ocxlflash_fs_cnt);
+	if (unlikely(rc < 0)) {
+		dev_err(dev, "%s: Cannot mount ocxlflash pseudofs =

rc=3D%d\n",

quoted

+			__func__, rc);
+		goto err2;
+	}
+
+	inode =3D alloc_anon_inode(ocxlflash_vfs_mount->mnt_sb);
+	if (IS_ERR(inode)) {
+		rc =3D PTR_ERR(inode);
+		dev_err(dev, "%s: alloc_anon_inode failed rc=3D%d\n",
+			__func__, rc);
+		goto err3;
+	}
+
+	this.name =3D name;
+	this.len =3D strlen(name);
+	this.hash =3D 0;
+	path.dentry =3D d_alloc_pseudo(ocxlflash_vfs_mount->mnt_sb, =

&this);

quoted

+	if (!path.dentry) {
+		dev_err(dev, "%s: d_alloc_pseudo failed\n", __func__);
+		rc =3D -ENOMEM;
+		goto err4;
+	}
+
+	path.mnt =3D mntget(ocxlflash_vfs_mount);
+	d_instantiate(path.dentry, inode);
+
+	file =3D alloc_file(&path, OPEN_FMODE(flags), fops);
+	if (IS_ERR(file)) {
+		rc =3D PTR_ERR(file);
+		dev_err(dev, "%s: alloc_file failed rc=3D%d\n",
+			__func__, rc);
+		goto err5;
+	}
+
+	file->f_flags =3D flags & (O_ACCMODE | O_NONBLOCK);
+	file->private_data =3D priv;
+out:
+	return file;
+err5:
+	path_put(&path);
+err4:
+	iput(inode);
+err3:
+	simple_release_fs(&ocxlflash_vfs_mount, &ocxlflash_fs_cnt);
+err2:
+	module_put(fops->owner);
+err1:
+	file =3D ERR_PTR(rc);
+	goto out;
+}
+
 /**
  * ocxlflash_set_master() - sets the context as master
  * @ctx_cookie:	Adapter context to set as master.

@@ -75,6 +206,7 @@ static void *ocxlflash_dev_context_init(struct =

pci_dev *pdev, void *afu_cookie)

quoted

 	ctx->pe =3D rc;
 	ctx->master =3D false;
+	ctx->mapping =3D NULL;
 	ctx->hw_afu =3D afu;
 out:
 	return ctx;

@@ -100,6 +232,7 @@ static int ocxlflash_release_context(void =

*ctx_cookie)

quoted

 		goto out;
 	idr_remove(&ctx->hw_afu->idr, ctx->pe);
+	ocxlflash_release_mapping(ctx);
 	kfree(ctx);
 out:
 	return rc;

@@ -262,6 +395,72 @@ static void *ocxlflash_create_afu(struct pci_dev =

*pdev)

quoted

 	goto out;
 }
+static const struct file_operations ocxl_afu_fops =3D {
+	.owner		=3D THIS_MODULE,
+};
+
+/**
+ * ocxlflash_get_fd() - get file descriptor for an adapter context
+ * @ctx_cookie:	Adapter context.
+ * @fops:	File operations to be associated.
+ * @fd:		File descriptor to be returned back.
+ *
+ * Return: pointer to the file on success, ERR_PTR on failure
+ */
+static struct file *ocxlflash_get_fd(void *ctx_cookie,
+				     struct file_operations *fops, int =

*fd)

quoted

+{
+	struct ocxlflash_context *ctx =3D ctx_cookie;
+	struct device *dev =3D ctx->hw_afu->dev;
+	struct file *file;
+	int flags, fdtmp;
+	int rc =3D 0;
+	char *name =3D NULL;
+
+	/* Only allow one fd per context */
+	if (ctx->mapping) {
+		dev_err(dev, "%s: Context is already mapped to an fd\n",
+			__func__);
+		rc =3D -EEXIST;
+		goto err1;
+	}
+
+	flags =3D O_RDWR | O_CLOEXEC;
+
+	/* This code is similar to anon_inode_getfd() */
+	rc =3D get_unused_fd_flags(flags);
+	if (unlikely(rc < 0)) {
+		dev_err(dev, "%s: get_unused_fd_flags failed rc=3D%d\n",
+			__func__, rc);
+		goto err1;
+	}
+	fdtmp =3D rc;
+
+	/* Use default ops if there is no fops */
+	if (!fops)
+		fops =3D (struct file_operations *)&ocxl_afu_fops;
+
+	name =3D kasprintf(GFP_KERNEL, "ocxlflash:%d", ctx->pe);
+	file =3D ocxlflash_getfile(dev, name, fops, ctx, flags);
+	kfree(name);
+	if (IS_ERR(file)) {
+		rc =3D PTR_ERR(file);
+		dev_err(dev, "%s: ocxlflash_getfile failed rc=3D%d\n",
+			__func__, rc);
+		goto err2;
+	}
+
+	ctx->mapping =3D file->f_mapping;
+	*fd =3D fdtmp;
+out:
+	return file;
+err2:
+	put_unused_fd(fdtmp);
+err1:
+	file =3D ERR_PTR(rc);
+	goto out;
+}
+
 /* Backend ops to ocxlflash services */
 const struct cxlflash_backend_ops cxlflash_ocxl_ops =3D {
 	.module			=3D THIS_MODULE,

@@ -271,4 +470,5 @@ const struct cxlflash_backend_ops =

cxlflash_ocxl_ops =3D {

quoted

 	.release_context	=3D ocxlflash_release_context,
 	.create_afu		=3D ocxlflash_create_afu,
 	.destroy_afu		=3D ocxlflash_destroy_afu,
+	.get_fd			=3D ocxlflash_get_fd,
 };

diff --git a/drivers/scsi/cxlflash/ocxl_hw.h =

b/drivers/scsi/cxlflash/ocxl_hw.h

quoted

index 0381682..7abc532 100644

--- a/drivers/scsi/cxlflash/ocxl_hw.h
+++ b/drivers/scsi/cxlflash/ocxl_hw.h

@@ -32,6 +32,7 @@ struct ocxl_hw_afu {
 struct ocxlflash_context {
 	struct ocxl_hw_afu *hw_afu;	/* HW AFU back pointer */
+	struct address_space *mapping;	/* Mapping for pseudo filesystem =

*/

quoted

 	bool master;			/* Whether this is a master =

context */

quoted

 	int pe;				/* Process element */
 };