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72 lines
3.4 KiB
72 lines
3.4 KiB
From 5bace483dedc9098da8191f39c823649948a7a3c Mon Sep 17 00:00:00 2001 |
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From: NeilBrown <neil@brown.name> |
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Date: Wed, 8 Nov 2017 19:29:32 +1100 |
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Subject: [PATCH] umount: always use MNT_FORCE in umount_all() (#7213) |
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The linux umount2() systemcall accepts a MNT_FORCE flags |
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which some filesystems honor, particularly FUSE and various |
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network filesystems such as NFS. |
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These filesystems can sometimes wait for an indefinite period |
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for a response from an external service, and the wait if |
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sometimes "uninterruptible" meaning that the process cannot be |
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killed. |
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Using MNT_FORCE causes any such request that are outstanding to |
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be aborted. This normally allows the waiting process to |
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be killed. It will then realease and reference it has to the |
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filesytem, this allowing the filesystem to be unmounted. |
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If there remain active references to the filesystem, MNT_FORCE |
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is *not* forcefull enough to unmount the filesystem anyway. |
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By the time that umount_all() is run by systemd-shutdown, all |
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filesystems *should* be unmounted, and sync() will have been |
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called. Anything that remains cannot be unmounted in a |
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completely clean manner and just nees to be dealt with as firmly |
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as possible. So use MNT_FORCE and try to explain why in the |
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comment. |
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Also enhance an earlier comment to explain why umount2() is |
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safe even though mount(MNT_REMOUNT) isn't. |
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(cherry picked from commit c44cac7c6c43407d28bd8daebff39f6145a2a33e) |
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Resolves: #1571098 |
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--- |
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src/core/umount.c | 16 +++++++++++----- |
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1 file changed, 11 insertions(+), 5 deletions(-) |
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diff --git a/src/core/umount.c b/src/core/umount.c |
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index 3eec0d459..91d67c06c 100644 |
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--- a/src/core/umount.c |
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+++ b/src/core/umount.c |
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@@ -377,7 +377,9 @@ static int mount_points_list_umount(MountPoint **head, bool *changed, bool log_e |
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the superblock here, not the bind mount. |
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If the filesystem is a network fs, also skip the |
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remount. It brings no value (we cannot leave |
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- a "dirty fs") and could hang if the network is down. */ |
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+ a "dirty fs") and could hang if the network is down. |
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+ Note that umount2() is more careful and will not |
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+ hang because of the network being down. */ |
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if (detect_container(NULL) <= 0 && |
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!fstype_is_network(m->type)) { |
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_cleanup_free_ char *options = NULL; |
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@@ -418,11 +420,15 @@ static int mount_points_list_umount(MountPoint **head, bool *changed, bool log_e |
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) |
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continue; |
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- /* Trying to umount. We don't force here since we rely |
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- * on busy NFS and FUSE file systems to return EBUSY |
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- * until we closed everything on top of them. */ |
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+ /* Trying to umount. Using MNT_FORCE causes some |
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+ * filesystems (e.g. FUSE and NFS and other network |
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+ * filesystems) to abort any pending requests and |
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+ * return -EIO rather than blocking indefinitely. |
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+ * If the filesysten is "busy", this may allow processes |
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+ * to die, thus making the filesystem less busy so |
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+ * the unmount might succeed (rather then return EBUSY).*/ |
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log_info("Unmounting %s.", m->path); |
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- if (umount2(m->path, 0) == 0) { |
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+ if (umount2(m->path, MNT_FORCE) == 0) { |
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if (changed) |
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*changed = true; |
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