49 lines
1.3 KiB
Diff
49 lines
1.3 KiB
Diff
From d9e6aef724ad0444ca59f536062b3ce3755ab8ff Mon Sep 17 00:00:00 2001
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From: Thomas Gleixner <tglx@linutronix.de>
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Date: Sun, 19 Jul 2009 08:44:27 -0500
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Subject: [PATCH 215/267] fs: namespace preemption fix
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On RT we cannot loop with preemption disabled here as
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mnt_make_readonly() might have been preempted. We can safely enable
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preemption while waiting for MNT_WRITE_HOLD to be cleared. Safe on !RT
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as well.
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Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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---
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fs/namespace.c | 10 +++++++---
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1 file changed, 7 insertions(+), 3 deletions(-)
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diff --git a/fs/namespace.c b/fs/namespace.c
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index cfc6d44..63fd6d7 100644
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--- a/fs/namespace.c
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+++ b/fs/namespace.c
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@@ -341,8 +341,14 @@ int mnt_want_write(struct vfsmount *mnt)
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* incremented count after it has set MNT_WRITE_HOLD.
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*/
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smp_mb();
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- while (mnt->mnt_flags & MNT_WRITE_HOLD)
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+ /*
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+ * No need to keep preemption disabled accross the spin loop.
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+ */
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+ while (mnt->mnt_flags & MNT_WRITE_HOLD) {
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+ preempt_enable();
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cpu_relax();
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+ preempt_disable();
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+ }
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/*
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* After the slowpath clears MNT_WRITE_HOLD, mnt_is_readonly will
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* be set to match its requirements. So we must not load that until
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@@ -352,9 +358,7 @@ int mnt_want_write(struct vfsmount *mnt)
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if (__mnt_is_readonly(mnt)) {
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mnt_dec_writers(mnt);
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ret = -EROFS;
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- goto out;
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}
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-out:
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preempt_enable();
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return ret;
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}
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--
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1.7.10
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