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List: lustre-devel
Subject: [lustre-devel] [PATCH v2 15/29] lustre: lprocfs: use log2.h macros instead of shift loop.
From: James Simmons <jsimmons () infradead ! org>
Date: 2019-05-20 12:50:57
Message-ID: 1558356671-29599-16-git-send-email-jsimmons () infradead ! org
[Download RAW message or body]
From: NeilBrown <neilb@suse.com>
These shift loops seem to be trying to avoid doing a
multiplication.
The same effect can be achieved more transparently using
rounddown_pow_of_two(). Even though there is a multiplication
in the C code, the resulting machine code just does a single shift.
As rounddown_pow_of_two() is not defined for 0, and as we cannot be
positively use the blk_size is non-zero, use blk_size ?: 1.
Signed-off-by: NeilBrown <neilb@suse.com>
---
fs/lustre/obdclass/lprocfs_status.c | 10 +++-------
1 file changed, 3 insertions(+), 7 deletions(-)
diff --git a/fs/lustre/obdclass/lprocfs_status.c b/fs/lustre/obdclass/lprocfs_status.c
index 29c6b5d..2af9dad 100644
--- a/fs/lustre/obdclass/lprocfs_status.c
+++ b/fs/lustre/obdclass/lprocfs_status.c
@@ -374,9 +374,7 @@ static ssize_t kbytestotal_show(struct kobject *kobj, struct attribute *attr,
u32 blk_size = osfs.os_bsize >> 10;
u64 result = osfs.os_blocks;
- while (blk_size >>= 1)
- result <<= 1;
-
+ result *= rounddown_pow_of_two(blk_size ?: 1);
return sprintf(buf, "%llu\n", result);
}
@@ -397,8 +395,7 @@ static ssize_t kbytesfree_show(struct kobject *kobj, struct attribute *attr,
u32 blk_size = osfs.os_bsize >> 10;
u64 result = osfs.os_bfree;
- while (blk_size >>= 1)
- result <<= 1;
+ result *= rounddown_pow_of_two(blk_size ?: 1);
return sprintf(buf, "%llu\n", result);
}
@@ -420,8 +417,7 @@ static ssize_t kbytesavail_show(struct kobject *kobj, struct attribute *attr,
u32 blk_size = osfs.os_bsize >> 10;
u64 result = osfs.os_bavail;
- while (blk_size >>= 1)
- result <<= 1;
+ result *= rounddown_pow_of_two(blk_size ?: 1);
return sprintf(buf, "%llu\n", result);
}
--
1.8.3.1
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