The logic is used to protect load/store tearing on 32 bit platforms,
for example, after i_size_read returned, there is no guarantee that
inode->size won't be changed. Therefore, READ/WRITE_ONCE suffice, which
is already implied by smp_load_acquire/smp_store_release.
Signed-off-by: Alex <alex.fcyrx@xxxxxxxxx>
---
include/linux/fs.h | 41 -----------------------------------------
1 file changed, 41 deletions(-)
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 4ec77da65f14..7f743881e20d 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -952,39 +952,10 @@ void filemap_invalidate_lock_two(struct address_space *mapping1,
void filemap_invalidate_unlock_two(struct address_space *mapping1,
struct address_space *mapping2);
-
-/*
- * NOTE: in a 32bit arch with a preemptable kernel and
- * an UP compile the i_size_read/write must be atomic
- * with respect to the local cpu (unlike with preempt disabled),
- * but they don't need to be atomic with respect to other cpus like in
- * true SMP (so they need either to either locally disable irq around
- * the read or for example on x86 they can be still implemented as a
- * cmpxchg8b without the need of the lock prefix). For SMP compiles
- * and 64bit archs it makes no difference if preempt is enabled or not.
- */
static inline loff_t i_size_read(const struct inode *inode)
{
-#if BITS_PER_LONG==32 && defined(CONFIG_SMP)
- loff_t i_size;
- unsigned int seq;
-
- do {
- seq = read_seqcount_begin(&inode->i_size_seqcount);
- i_size = inode->i_size;
- } while (read_seqcount_retry(&inode->i_size_seqcount, seq));
- return i_size;
-#elif BITS_PER_LONG==32 && defined(CONFIG_PREEMPTION)
- loff_t i_size;
-
- preempt_disable();
- i_size = inode->i_size;
- preempt_enable();
- return i_size;
-#else
/* Pairs with smp_store_release() in i_size_write() */
return smp_load_acquire(&inode->i_size);
-#endif
}
/*
@@ -994,24 +965,12 @@ 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();
- write_seqcount_begin(&inode->i_size_seqcount);
- inode->i_size = i_size;
- write_seqcount_end(&inode->i_size_seqcount);
- preempt_enable();
-#elif BITS_PER_LONG==32 && defined(CONFIG_PREEMPTION)
- preempt_disable();
- inode->i_size = i_size;
- preempt_enable();
-#else
/*
* Pairs with smp_load_acquire() in i_size_read() to ensure
* changes related to inode size (such as page contents) are
* visible before we see the changed inode size.
*/
smp_store_release(&inode->i_size, i_size);
-#endif
}
static inline unsigned iminor(const struct inode *inode)
--
2.48.1
