USB: gadget: storage: optional SCSI WRITE FUA bit

MS Windows mounts removable storage in "Removal optimized mode" by
default. All the writes to the media are synchronous which is achieved
by setting FUA (Force Unit Access) bit in SCSI WRITE(10,12) commands.
This prevents I/O requests aggregation in block layer dramatically
decreasing performance.

This patch brings an option to accept or ignore mentioned bit
 a) via specifying module parameter "nofua", or
 b) through sysfs entry
	/sys/devices/platform/_UDC_/gadget/gadget-lunX/nofua
	(_UDC_ is the name of the USB Device Controller driver)

Patch is based on the work that was done by Denis Karpov for Maemo 5
platform.

Signed-off-by: Andy Shevchenko <ext-andriy.shevchenko@nokia.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Cc: Denis Karpov <ext-denis.2.karpov@nokia.com>
Cc: Adrian Hunter <adrian.hunter@nokia.com>
Cc: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 24 insertions, 7 deletions

diff --git a/drivers/usb/gadget/file_storage.c b/drivers/usb/gadget/file_storage.c
index d57c09f764d6..88e5ad2bc710 100644
--- a/drivers/usb/gadget/file_storage.c
+++ b/drivers/usb/gadget/file_storage.c
@@ -93,6 +93,8 @@
  *      removable               Default false, boolean for removable media
  *      luns=N                  Default N = number of filenames, number of
  *                                      LUNs to support
+ *      nofua=b[,b...]          Default false, booleans for ignore FUA flag
+ *                                      in SCSI WRITE(10,12) commands
  *      stall                   Default determined according to the type of
  *                                      USB device controller (usually true),
  *                                      boolean to permit the driver to halt
@@ -112,12 +114,12 @@
  *                                      PAGE_CACHE_SIZE)
  *
  * If CONFIG_USB_FILE_STORAGE_TEST is not set, only the "file", "ro",
- * "removable", "luns", "stall", and "cdrom" options are available; default
- * values are used for everything else.
+ * "removable", "luns", "nofua", "stall", and "cdrom" options are available;
+ * default values are used for everything else.
  *
  * The pathnames of the backing files and the ro settings are available in
- * the attribute files "file" and "ro" in the lun<n> subdirectory of the
- * gadget's sysfs directory.  If the "removable" option is set, writing to
+ * the attribute files "file", "nofua", and "ro" in the lun<n> subdirectory of
+ * the gadget's sysfs directory.  If the "removable" option is set, writing to
  * these files will simulate ejecting/loading the medium (writing an empty
  * line means eject) and adjusting a write-enable tab.  Changes to the ro
  * setting are not allowed when the medium is loaded or if CD-ROM emulation
@@ -304,8 +306,10 @@ MODULE_LICENSE("Dual BSD/GPL");
 static struct {
         char            *file[FSG_MAX_LUNS];
         int             ro[FSG_MAX_LUNS];
+        int             nofua[FSG_MAX_LUNS];
         unsigned int    num_filenames;
         unsigned int    num_ros;
+        unsigned int    num_nofuas;
         unsigned int    nluns;
 
         int             removable;
@@ -345,6 +349,10 @@ MODULE_PARM_DESC(file, "names of backing files or devices");
 module_param_array_named(ro, mod_data.ro, bool, &mod_data.num_ros, S_IRUGO);
 MODULE_PARM_DESC(ro, "true to force read-only");
 
+module_param_array_named(nofua, mod_data.nofua, bool, &mod_data.num_nofuas,
+                S_IRUGO);
+MODULE_PARM_DESC(nofua, "true to ignore SCSI WRITE(10,12) FUA bit");
+
 module_param_named(luns, mod_data.nluns, uint, S_IRUGO);
 MODULE_PARM_DESC(luns, "number of LUNs");
 
@@ -1279,7 +1287,8 @@ static int do_write(struct fsg_dev *fsg)
                         curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
                         return -EINVAL;
                 }
-                if (fsg->cmnd[1] & 0x08) {      // FUA
+                /* FUA */
+                if (!curlun->nofua && (fsg->cmnd[1] & 0x08)) {
                         spin_lock(&curlun->filp->f_lock);
                         curlun->filp->f_flags |= O_DSYNC;
                         spin_unlock(&curlun->filp->f_lock);
@@ -3133,6 +3142,7 @@ static int fsg_main_thread(void *fsg_)
 
 /* The write permissions and store_xxx pointers are set in fsg_bind() */
 static DEVICE_ATTR(ro, 0444, fsg_show_ro, NULL);
+static DEVICE_ATTR(nofua, 0644, fsg_show_nofua, NULL);
 static DEVICE_ATTR(file, 0444, fsg_show_file, NULL);
 
 
@@ -3362,6 +3372,10 @@ static int __ref fsg_bind(struct usb_gadget *gadget)
                 }
         }
 
+        /* Only for removable media? */
+        dev_attr_nofua.attr.mode = 0644;
+        dev_attr_nofua.store = fsg_store_nofua;
+
         /* Find out how many LUNs there should be */
         i = mod_data.nluns;
         if (i == 0)
@@ -3387,6 +3401,7 @@ static int __ref fsg_bind(struct usb_gadget *gadget)
                 curlun->ro = mod_data.cdrom || mod_data.ro[i];
                 curlun->initially_ro = curlun->ro;
                 curlun->removable = mod_data.removable;
+                curlun->nofua = mod_data.nofua[i];
                 curlun->dev.release = lun_release;
                 curlun->dev.parent = &gadget->dev;
                 curlun->dev.driver = &fsg_driver.driver;
@@ -3401,6 +3416,8 @@ static int __ref fsg_bind(struct usb_gadget *gadget)
                 if ((rc = device_create_file(&curlun->dev,
                                         &dev_attr_ro)) != 0 ||
                                 (rc = device_create_file(&curlun->dev,
+                                        &dev_attr_nofua)) != 0 ||
+                                (rc = device_create_file(&curlun->dev,
                                         &dev_attr_file)) != 0) {
                         device_unregister(&curlun->dev);
                         goto out;
@@ -3525,8 +3542,8 @@ static int __ref fsg_bind(struct usb_gadget *gadget)
                                 if (IS_ERR(p))
                                         p = NULL;
                         }
-                        LINFO(curlun, "ro=%d, file: %s\n",
-                                        curlun->ro, (p ? p : "(error)"));
+                        LINFO(curlun, "ro=%d, nofua=%d, file: %s\n",
+                              curlun->ro, curlun->nofua, (p ? p : "(error)"));
                 }
         }
         kfree(pathbuf);