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Subject[PATCH RESEND V5,1/2] mm: fadvise: move 'endbyte' calculations to helper function
Date
From: Charan Teja Reddy <quic_charante@quicinc.com>

Move the 'endbyte' calculations that determines last byte that fadvise
can to a helper function. This is a preparatory change made for
shmem_fadvise() functionality in the next patch. No functional changes
in this patch.

Signed-off-by: Charan Teja Reddy <quic_charante@quicinc.com>
---
Changes in V5:
-- Moved the 'endbyte' calculation to a helper function.
-- This patch is newly raised in V5 thus no change exists from v1 to v4.

mm/fadvise.c | 11 +----------
mm/internal.h | 21 +++++++++++++++++++++
2 files changed, 22 insertions(+), 10 deletions(-)

diff --git a/mm/fadvise.c b/mm/fadvise.c
index 338f160..0c82be2 100644
--- a/mm/fadvise.c
+++ b/mm/fadvise.c
@@ -65,16 +65,7 @@ int generic_fadvise(struct file *file, loff_t offset, loff_t len, int advice)
return 0;
}

- /*
- * Careful about overflows. Len == 0 means "as much as possible". Use
- * unsigned math because signed overflows are undefined and UBSan
- * complains.
- */
- endbyte = (u64)offset + (u64)len;
- if (!len || endbyte < len)
- endbyte = -1;
- else
- endbyte--; /* inclusive */
+ endbyte = fadvise_calc_endbyte(offset, len);

switch (advice) {
case POSIX_FADV_NORMAL:
diff --git a/mm/internal.h b/mm/internal.h
index 58dc6ad..b02f07e 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -546,6 +546,27 @@ static inline void vunmap_range_noflush(unsigned long start, unsigned long end)
#endif /* !CONFIG_MMU */

/*
+ * Helper function to get the endbyte of a file that fadvise can operate on.
+ */
+static inline loff_t fadvise_calc_endbyte(loff_t offset, loff_t len)
+{
+ loff_t endbyte;
+
+ /*
+ * Careful about overflows. Len == 0 means "as much as possible". Use
+ * unsigned math because signed overflows are undefined and UBSan
+ * complains.
+ */
+ endbyte = (u64)offset + (u64)len;
+ if (!len || endbyte < len)
+ endbyte = -1;
+ else
+ endbyte--; /* inclusive */
+
+ return endbyte;
+}
+
+/*
* Return the mem_map entry representing the 'offset' subpage within
* the maximally aligned gigantic page 'base'. Handle any discontiguity
* in the mem_map at MAX_ORDER_NR_PAGES boundaries.
--
2.7.4
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