linux-kernel - [PATCH V6 1/2] mm: fadvise: move 'endbyte' calculations to helper function

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Message-ID: <f33155c964c2485b0d9217617a21ef1759f90884.1675690847.git.quic_charante@quicinc.com>
Date:   Mon, 6 Feb 2023 19:51:32 +0530
From:   Charan Teja Kalla <quic_charante@...cinc.com>
To:     <akpm@...ux-foundation.org>, <hughd@...gle.com>,
        <willy@...radead.org>, <markhemm@...glemail.com>,
        <rientjes@...gle.com>, <surenb@...gle.com>, <shakeelb@...gle.com>,
        <mhocko@...e.com>, <vbabka@...e.cz>, <quic_pkondeti@...cinc.com>
CC:     <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
        Charan Teja Kalla <quic_charante@...cinc.com>
Subject: [PATCH V6 1/2] mm: fadvise: move 'endbyte' calculations to helper function

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 Kalla <quic_charante@...cinc.com>
---
 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 bf04fec..10169c6 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 = LLONG_MAX;
-	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 bcf75a8..47858af 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -637,6 +637,27 @@ 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 = LLONG_MAX;
+	else
+		endbyte--;		/* inclusive */
+
+	return endbyte;
+}
+
 /* Memory initialisation debug and verification */
 enum mminit_level {
 	MMINIT_WARNING,
-- 
2.7.4