[parted-devel] [PATCH] libparted: Use read only when probing devices on linux (#1245144)

[Brian C. Lane]

When a device is opened for RW closing it can trigger other actions,
like udev scanning it for partition changes. Use read only for the
init_* methods and RW for actual changes to the device.

This adds _device_open which takes mode flags as an argument and turns
linux_open into a wrapper for it with RW_MODE.

_device_open_ro is added to open the device with RD_MODE and increment
the open_counter. This is used in the init_* functions.

_device_close is a wrapper around linux_close that decrements the
open_counter and is used in the init_* functions.

All of these changes are self-contained with no external API changes.
The only visible change in behavior is that when a new PedDevice is
created the device is opened in RO_MODE instead of RW_MODE.

Resolves: rhbz#1245144
---
 libparted/arch/linux.c | 62 +++++++++++++++++++++++++++++++++++---------------
 1 file changed, 44 insertions(+), 18 deletions(-)

diff --git a/libparted/arch/linux.c b/libparted/arch/linux.c
index 349442b..6365111 100644
--- a/libparted/arch/linux.c
+++ b/libparted/arch/linux.c
@@ -291,7 +291,9 @@ struct blkdev_ioctl_param {
 static char* _device_get_part_path (PedDevice const *dev, int num);
 static int _partition_is_mounted_by_path (const char* path);
 static unsigned int _device_get_partition_range(PedDevice const* dev);
-
+static int _device_open (PedDevice* dev, int flags);
+static int _device_open_ro (PedDevice* dev);
+static int _device_close (PedDevice* dev);
 
 static int
 _read_fd (int fd, char **buf)
@@ -910,7 +912,7 @@ init_ide (PedDevice* dev)
         if (!_device_stat (dev, &dev_stat))
                 goto error;
 
-        if (!ped_device_open (dev))
+        if (!_device_open_ro (dev))
                 goto error;
 
         if (ioctl (arch_specific->fd, HDIO_GET_IDENTITY, &hdi)) {
@@ -979,11 +981,11 @@ init_ide (PedDevice* dev)
         if (!_device_probe_geometry (dev))
                 goto error_close_dev;
 
-        ped_device_close (dev);
+        _device_close (dev);
         return 1;
 
 error_close_dev:
-        ped_device_close (dev);
+        _device_close (dev);
 error:
         return 0;
 }
@@ -1116,7 +1118,7 @@ init_scsi (PedDevice* dev)
         char* vendor;
         char* product;
 
-        if (!ped_device_open (dev))
+        if (!_device_open_ro (dev))
                 goto error;
 
         if (ioctl (arch_specific->fd, SCSI_IOCTL_GET_IDLUN, &idlun) < 0) {
@@ -1130,7 +1132,7 @@ init_scsi (PedDevice* dev)
                         goto error_close_dev;
                 if (!_device_probe_geometry (dev))
                         goto error_close_dev;
-                ped_device_close (dev);
+                _device_close (dev);
                 return 1;
         }
 
@@ -1152,11 +1154,11 @@ init_scsi (PedDevice* dev)
         if (!_device_probe_geometry (dev))
                 goto error_close_dev;
 
-        ped_device_close (dev);
+        _device_close (dev);
         return 1;
 
 error_close_dev:
-        ped_device_close (dev);
+        _device_close (dev);
 error:
         return 0;
 }
@@ -1168,7 +1170,7 @@ init_file (PedDevice* dev)
 
         if (!_device_stat (dev, &dev_stat))
                 goto error;
-        if (!ped_device_open (dev))
+        if (!_device_open_ro (dev))
                 goto error;
 
         dev->sector_size = PED_SECTOR_SIZE_DEFAULT;
@@ -1195,7 +1197,7 @@ init_file (PedDevice* dev)
                 goto error_close_dev;
         }
 
-        ped_device_close (dev);
+        _device_close (dev);
 
         dev->bios_geom.cylinders = dev->length / 4 / 32;
         dev->bios_geom.heads = 4;
@@ -1206,7 +1208,7 @@ init_file (PedDevice* dev)
         return 1;
 
 error_close_dev:
-        ped_device_close (dev);
+        _device_close (dev);
 error:
         return 0;
 }
@@ -1222,7 +1224,7 @@ init_dasd (PedDevice* dev, const char* model_name)
         if (!_device_stat (dev, &dev_stat))
                 goto error;
 
-        if (!ped_device_open (dev))
+        if (!_device_open_ro (dev))
                 goto error;
 
         LinuxSpecific* arch_specific = LINUX_SPECIFIC (dev);
@@ -1262,11 +1264,11 @@ init_dasd (PedDevice* dev, const char* model_name)
 
         dev->model = strdup (model_name);
 
-        ped_device_close (dev);
+        _device_close (dev);
         return 1;
 
 error_close_dev:
-        ped_device_close (dev);
+        _device_close (dev);
 error:
         return 0;
 }
@@ -1281,7 +1283,7 @@ init_generic (PedDevice* dev, const char* model_name)
         if (!_device_stat (dev, &dev_stat))
                 goto error;
 
-        if (!ped_device_open (dev))
+        if (!_device_open_ro (dev))
                 goto error;
 
         ped_exception_fetch_all ();
@@ -1329,11 +1331,11 @@ init_generic (PedDevice* dev, const char* model_name)
 
         dev->model = strdup (model_name);
 
-        ped_device_close (dev);
+        _device_close (dev);
         return 1;
 
 error_close_dev:
-        ped_device_close (dev);
+        _device_close (dev);
 error:
         return 0;
 }
@@ -1620,12 +1622,27 @@ retry:
 }
 
 static int
+_device_open_ro (PedDevice* dev)
+{
+    int rc = _device_open (dev, RD_MODE);
+    if (rc)
+        dev->open_count++;
+    return rc;
+}
+
+static int
 linux_open (PedDevice* dev)
 {
+    return _device_open (dev, RW_MODE);
+}
+
+static int
+_device_open (PedDevice* dev, int flags)
+{
         LinuxSpecific*  arch_specific = LINUX_SPECIFIC (dev);
 
 retry:
-        arch_specific->fd = open (dev->path, RW_MODE);
+        arch_specific->fd = open (dev->path, flags);
 
         if (arch_specific->fd == -1) {
                 char*   rw_error_msg = strerror (errno);
@@ -1694,6 +1711,15 @@ linux_refresh_close (PedDevice* dev)
         return 1;
 }
 
+static int
+_device_close (PedDevice* dev)
+{
+    int rc = linux_close (dev);
+    if (dev->open_count > 0)
+        dev->open_count--;
+    return rc;
+}
+
 #if SIZEOF_OFF_T < 8
 
 static _syscall5(int,_llseek,
-- 
2.4.3