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btrfs: Use unified stripe_page's index calculation

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We are using different index calculation method for stripe_page in
current code:
1: (rbio->stripe_len / PAGE_CACHE_SIZE) * stripe_index + page_index
2: DIV_ROUND_UP(rbio->stripe_len, PAGE_CACHE_SIZE) * stripe_index + page_index
3: DIV_ROUND_UP(rbio->stripe_len * stripe_index, PAGE_CACHE_SIZE) + page_index
...

They can get same result when stripe_len align to PAGE_CACHE_SIZE,
this is why current code can work, intruduce and use a common function
for calculation is a better choose.

Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Signed-off-by: Chris Mason <clm@fb.com>
This commit is contained in:
Zhao Lei 2015-03-03 20:38:46 +08:00 committed by Chris Mason
parent bfca9a6d4b
commit b7178a5f03
1 changed files with 21 additions and 22 deletions
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43
fs/btrfs/raid56.c
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@ -609,13 +609,28 @@ static int rbio_can_merge(struct btrfs_raid_bio *last,
return 1;
}
static int rbio_stripe_page_index(struct btrfs_raid_bio *rbio, int stripe,
int index)
{
return stripe * rbio->stripe_npages + index;
}
/*
* these are just the pages from the rbio array, not from anything
* the FS sent down to us
*/
static struct page *rbio_stripe_page(struct btrfs_raid_bio *rbio, int stripe,
int index)
{
return rbio->stripe_pages[rbio_stripe_page_index(rbio, stripe, index)];
}
/*
* helper to index into the pstripe
*/
static struct page *rbio_pstripe_page(struct btrfs_raid_bio *rbio, int index)
{
index += (rbio->nr_data * rbio->stripe_len) >> PAGE_CACHE_SHIFT;
return rbio->stripe_pages[index];
return rbio_stripe_page(rbio, rbio->nr_data, index);
}
/*
@ -626,10 +641,7 @@ static struct page *rbio_qstripe_page(struct btrfs_raid_bio *rbio, int index)
{
if (rbio->nr_data + 1 == rbio->real_stripes)
return NULL;
index += ((rbio->nr_data + 1) * rbio->stripe_len) >>
PAGE_CACHE_SHIFT;
return rbio->stripe_pages[index];
return rbio_stripe_page(rbio, rbio->nr_data + 1, index);
}
/*
@ -947,8 +959,7 @@ static struct page *page_in_rbio(struct btrfs_raid_bio *rbio,
*/
static unsigned long rbio_nr_pages(unsigned long stripe_len, int nr_stripes)
{
unsigned long nr = stripe_len * nr_stripes;
return DIV_ROUND_UP(nr, PAGE_CACHE_SIZE);
return DIV_ROUND_UP(stripe_len, PAGE_CACHE_SIZE) * nr_stripes;
}
/*
@ -1026,13 +1037,13 @@ static int alloc_rbio_pages(struct btrfs_raid_bio *rbio)
return 0;
}
/* allocate pages for just the p/q stripes */
/* only allocate pages for p/q stripes */
static int alloc_rbio_parity_pages(struct btrfs_raid_bio *rbio)
{
int i;
struct page *page;
i = (rbio->nr_data * rbio->stripe_len) >> PAGE_CACHE_SHIFT;
i = rbio_stripe_page_index(rbio, rbio->nr_data, 0);
for (; i < rbio->nr_pages; i++) {
if (rbio->stripe_pages[i])
@ -1120,18 +1131,6 @@ static void validate_rbio_for_rmw(struct btrfs_raid_bio *rbio)
}
}
/*
* these are just the pages from the rbio array, not from anything
* the FS sent down to us
*/
static struct page *rbio_stripe_page(struct btrfs_raid_bio *rbio, int stripe, int page)
{
int index;
index = stripe * (rbio->stripe_len >> PAGE_CACHE_SHIFT);
index += page;
return rbio->stripe_pages[index];
}
/*
* helper function to walk our bio list and populate the bio_pages array with
* the result. This seems expensive, but it is faster than constantly