[PATCH RT 17/25][RFC 3.0.23-rt39-rc1] fs: Protect open coded isize seqcount

[Steven Rostedt]

From: Thomas Gleixner <tglx@xxxxxxxxxxxxx>

A writer might be preempted in the write side critical section on
RT. Disable preemption to avoid endless spinning of a preempting
reader.

Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: stable-rt@xxxxxxxxxxxxxxx
Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
---
 include/linux/fs.h |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 9c85217..c7984a5 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -876,9 +876,11 @@ static inline loff_t i_size_read(const struct inode *inode)
 static inline void i_size_write(struct inode *inode, loff_t i_size)
 {
 #if BITS_PER_LONG==32 && defined(CONFIG_SMP)
+	preempt_disable_rt();
 	write_seqcount_begin(&inode->i_size_seqcount);
 	inode->i_size = i_size;
 	write_seqcount_end(&inode->i_size_seqcount);
+	preempt_enable_rt();
 #elif BITS_PER_LONG==32 && defined(CONFIG_PREEMPT)
 	preempt_disable();
 	inode->i_size = i_size;
-- 
1.7.8.3


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