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From 1edbfcdb4a973120048b5c04e0eb92b05ad3cbd2 Mon Sep 17 00:00:00 2001
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From: Vratislav Podzimek <vpodzime@redhat.com>
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Date: Wed, 26 Oct 2016 16:13:58 +0200
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Subject: [PATCH] Open the device file as RDWR when committing parts
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We block udev from generating events for the device while we are between
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committing changes to disk and informing kernel about the changes. If we close
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the file descriptor later, no udev changes are generated either unless we open
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is as RDWR. Here's the difference:
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RDONLY:
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# udevadm monitor
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monitor will print the received events for:
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UDEV - the event which udev sends out after rule processing
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KERNEL - the kernel uevent
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KERNEL[68221.911864] change /devices/virtual/block/loop0 (block)
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KERNEL[68221.913442] change /devices/virtual/block/loop0 (block)
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KERNEL[68221.913794] add /devices/virtual/block/loop0/loop0p1 (block)
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KERNEL[68221.915019] change /devices/virtual/block/loop0 (block)
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KERNEL[68221.915217] change /devices/virtual/block/loop0/loop0p1 (block)
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UDEV [68221.941293] change /devices/virtual/block/loop0 (block)
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UDEV [68221.954214] change /devices/virtual/block/loop0/loop0p1 (block)
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RDWR:
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# udevadm monitor
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monitor will print the received events for:
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UDEV - the event which udev sends out after rule processing
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KERNEL - the kernel uevent
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KERNEL[68161.533114] change /devices/virtual/block/loop0 (block)
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KERNEL[68161.533165] change /devices/virtual/block/loop0 (block)
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UDEV [68161.533219] change /devices/virtual/block/loop0 (block)
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KERNEL[68161.533262] add /devices/virtual/block/loop0/loop0p1 (block)
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KERNEL[68161.533292] change /devices/virtual/block/loop0 (block)
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KERNEL[68161.533326] change /devices/virtual/block/loop0/loop0p1 (block)
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UDEV [68161.539255] add /devices/virtual/block/loop0/loop0p1 (block)
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UDEV [68161.560215] change /devices/virtual/block/loop0 (block)
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UDEV [68161.572345] change /devices/virtual/block/loop0/loop0p1 (block)
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As seen above, there's no 'add' udev event in case we open the device file as
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RDONLY.
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(cherry picked from commit 44fdb3953eb05ff4f43a576f15d508928dca3eb7)
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Signed-off-by: Vratislav Podzimek <vpodzime@redhat.com>
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---
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src/plugins/part.c | 5 ++++-
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1 file changed, 4 insertions(+), 1 deletion(-)
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diff --git a/src/plugins/part.c b/src/plugins/part.c
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index d5239e3..0f8e678 100644
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--- a/src/plugins/part.c
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+++ b/src/plugins/part.c
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@@ -157,7 +157,7 @@ static gboolean disk_commit (PedDisk *disk, gchar *path, GError **error) {
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/* XXX: try to grab an exclusive lock for the device so that udev doesn't
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trigger events for it in between the two operations we need to perform
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(see below) */
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- dev_fd = open (disk->dev->path, O_RDONLY|O_CLOEXEC);
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+ dev_fd = open (disk->dev->path, O_RDWR|O_CLOEXEC);
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if (dev_fd >= 0)
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/* if this fails, we can do no better anyway, so just ignore the return
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value */
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@@ -167,6 +167,7 @@ static gboolean disk_commit (PedDisk *disk, gchar *path, GError **error) {
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if (ret == 0) {
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set_parted_error (error, BD_PART_ERROR_FAIL);
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g_prefix_error (error, "Failed to commit changes to device '%s'", path);
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+ flock (dev_fd, LOCK_UN);
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close (dev_fd);
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return FALSE;
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}
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@@ -175,10 +176,12 @@ static gboolean disk_commit (PedDisk *disk, gchar *path, GError **error) {
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if (ret == 0) {
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set_parted_error (error, BD_PART_ERROR_FAIL);
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g_prefix_error (error, "Failed to inform OS about changes on the '%s' device", path);
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+ flock (dev_fd, LOCK_UN);
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close (dev_fd);
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return FALSE;
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}
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+ flock (dev_fd, LOCK_UN);
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close (dev_fd);
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return TRUE;
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}
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--
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2.7.4
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