>From d45ed0d6cb2519464807f4185a5ad1644e802507 Mon Sep 17 00:00:00 2001
From: Phillip Susi <psusi@cfl.rr.com>
Date: Wed, 30 Nov 2011 21:24:45 -0500
Subject: [PATCH] Avoid the HDIO_GETGEO when possible

We were using the long depreciated HDIO_GETGEO ioctl on the
partition to get its start sector.  Use the new BLKPG_GET_PARTITION
ioctl instead.  This allows for disks > 2TB and partitioned loop
devices, which don't support HDIO_GETGEO.  As a fallback when
BLKPG_GET_PARTITION fails or is not availible, try getting the
values from sysfs, and finally use BLKGETSIZE64 and HDIO_GETGEO
as a last resort.

This modifies and superceeds Petr Uzel's patch:
libparted: fix reading partition start sector from kernel
---
 libparted/arch/linux.c |  124 ++++++++++++++++++++++++++++++++++++++++-------
 1 files changed, 105 insertions(+), 19 deletions(-)

diff --git a/libparted/arch/linux.c b/libparted/arch/linux.c
index 3799b9d..2d10b80 100644
--- a/libparted/arch/linux.c
+++ b/libparted/arch/linux.c
@@ -2410,6 +2410,25 @@ _blkpg_remove_partition (PedDisk* disk, int n)
                                     BLKPG_DEL_PARTITION);
 }
 
+#ifdef BLKPG_GET_PARTITION
+static int
+_blkpg_get_partition (PedPartition *part, long long *start, long long *length)
+{
+        struct blkpg_partition  linux_part;
+        int ret;
+
+        memset (&linux_part, 0, sizeof (linux_part));
+        linux_part.pno = part->num;
+        if (_blkpg_part_command (part->disk->dev, &linux_part,
+                                 BLKPG_GET_PARTITION))
+        {
+                *start = linux_part.start;
+                *length = linux_part.length;
+                return 1;
+        } else return 0;
+}
+#endif
+
 /* Read the integer from /sys/block/DEV_BASE/ENTRY and set *VAL
    to that value, where DEV_BASE is the last component of DEV->path.
    Upon success, return true.  Otherwise, return false. */
@@ -2432,6 +2451,85 @@ _sysfs_int_entry_from_dev(PedDevice const* dev, const char *entry, int *val)
         return ok;
 }
 
+/* Read the unsigned long long from /sys/block/DEV_BASE/PART_BASE/ENTRY
+   and set *VAL to that value, where DEV_BASE is the last component of path to
+   block device corresponding to PART and PART_BASE is the sysfs name of PART.
+   Upon success, return true. Otherwise, return false. */
+static bool
+_sysfs_ull_entry_from_part(PedPartition const* part, const char *entry, unsigned long long *val)
+{
+        char path[128];
+        char *part_name = linux_partition_get_path(part);
+        if (!part_name)
+                return false;
+
+        int r = snprintf(path, sizeof(path), "/sys/block/%s/%s/%s",
+                last_component(part->disk->dev->path),
+                last_component(part_name), entry);
+        free(part_name);
+        if (r < 0 || r >= sizeof(path))
+                return false;
+
+        FILE *fp = fopen(path, "r");
+        if (!fp)
+                return false;
+
+        bool ok = fscanf(fp, "%llu", val) == 1;
+        fclose(fp);
+
+        return ok;
+}
+
+
+/* Get the starting sector and length of a partition PART within a block device
+ * Use blkpg if availible, then check sysfs and then use HDIO_GETGEO and BLKGETSIZE64
+ * ioctls as fallback. Upon success, return true. Otherwise, return false. */
+static bool
+_kernel_get_partition_start_and_legnth(PedPartition const *part, unsigned long long *start,
+                                      unsigned long long *length)
+{
+        int fd = -1;
+        int ok;
+        PED_ASSERT(part);
+        PED_ASSERT(start);
+        PED_ASSERT(length);
+        
+#ifdef BLKPG_GET_PARTITION
+        ok = _blkpg_get_partition (part, start, length);
+        if (ok)
+                return ok;
+#endif
+        char *dev_name = linux_partition_get_path (part);
+        if (!dev_name)
+                return false;
+
+        ok = _sysfs_ull_entry_from_part (part, "start", start);
+        if (!ok) {
+                struct hd_geometry geom;
+                int fd = open (dev_name, O_RDONLY);
+                if (fd != -1 && ioctl (fd, HDIO_GETGEO, &geom)) {
+                        *val = geom.start;
+                        ok = true;
+        }
+        ok = _sysfs_ull_entry_from_part (part, "size", length);
+        if (!ok)
+        {
+                if (fd == -1)
+                        fd = open (dev_name, O_RDONLY);
+                if (fd != -1 && ioctl (fd, BLKGETSIZE64, length))
+                        ok = true;
+        }
+        if (ok)
+                *length /= part->disk->dev->sector_size;
+        if (fd != -1)
+                close (fd);
+
+        free (dev_name);
+        return ok;
+}
+
+
+
 /*
  * The number of partitions that a device can have depends on the kernel.
  * If we don't find this value in /sys/block/DEV/ext_range, we will use our own
@@ -2519,30 +2617,18 @@ _disk_sync_part_table (PedDisk* disk)
                 const PedPartition *part = ped_disk_get_partition (disk, i);
                 if (part) {
                         if (!ok[i - 1] && errnums[i - 1] == EBUSY) {
-                                struct hd_geometry geom;
-                                unsigned long long length = 0;
+                                unsigned long long length;
+                                unsigned long long start;
                                 /* get start and length of existing partition */
-                                char *dev_name = _device_get_part_path (disk->dev, i);
-                                if (!dev_name)
-                                        goto cleanup;
-                                int fd = open (dev_name, O_RDONLY);
-                                if (fd == -1
-				    || ioctl (fd, HDIO_GETGEO, &geom)
-				    || ioctl (fd, BLKGETSIZE64, &length)) {
+                                if (!_kernel_get_partition_start_and_length(part, &start, &length)) {
                                         ped_exception_throw (
-                                                             PED_EXCEPTION_BUG,
-                                                             PED_EXCEPTION_CANCEL,
+                                                PED_EXCEPTION_BUG,
+                                                PED_EXCEPTION_CANCEL,
 			    _("Unable to determine the size and length of %s."),
-                                                             dev_name);
-                                        if (fd != -1)
-                                                close (fd);
-                                        free (dev_name);
+                                                dev_name);
                                         goto cleanup;
                                 }
-                                free (dev_name);
-                                length /= disk->dev->sector_size;
-                                close (fd);
-                                if (geom.start == part->geom.start
+                                if (start == part->geom.start
 				    && length == part->geom.length)
                                         ok[i - 1] = 1;
                                 /* If the new partition is unchanged and the
-- 
1.7.5.4

