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exofs: Prepare for groups
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* Rename _offset_dev_unit_off() to _calc_stripe_info()
  and recieve a struct for the output params

* In _prepare_for_striping we only need to call
  _calc_stripe_info() once. The other componets
  are easy to calculate from that. This code
  was inspired by what's done in truncate.

* Some code shifts that make sense now but will make
  more sense when group support is added.

Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>
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Boaz Harrosh committed Feb 28, 2010
1 parent 96391e2 commit b367e78
Showing 1 changed file with 99 additions and 60 deletions.
159 changes: 99 additions & 60 deletions fs/exofs/ios.c
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Original file line number Diff line number Diff line change
Expand Up @@ -259,28 +259,46 @@ int exofs_check_io(struct exofs_io_state *ios, u64 *resid)
return acumulated_lin_err;
}

/* REMOVEME: After review
Some quoteing from the standard
L = logical offset into the file
W = number of data components in a stripe
S = W * stripe_unit (S is Stripe length)
N = L / S (N is the stripe Number)
C = (L-(N*S)) / stripe_unit (C is the component)
O = (N*stripe_unit)+(L%stripe_unit) (O is the object's offset)
*/

static void _offset_dev_unit_off(struct exofs_io_state *ios, u64 file_offset,
u64 *obj_offset, unsigned *dev, unsigned *unit_off)
/*
* L - logical offset into the file
*
* U - The number of bytes in a full stripe
*
* U = stripe_unit * group_width
*
* N - The stripe number
*
* N = L / U
*
* C - The component index coresponding to L
*
* C = (L - (N*U)) / stripe_unit
*
* O - The component offset coresponding to L
*
* (N*stripe_unit)+(L%stripe_unit)
*/

struct _striping_info {
u64 obj_offset;
unsigned dev;
unsigned unit_off;
};

static void _calc_stripe_info(struct exofs_io_state *ios, u64 file_offset,
struct _striping_info *si)
{
unsigned stripe_unit = ios->layout->stripe_unit;
unsigned stripe_length = stripe_unit * ios->layout->group_width;
u64 stripe_no = file_offset;
unsigned stripe_mod = do_div(stripe_no, stripe_length);
u32 stripe_unit = ios->layout->stripe_unit;
u32 group_width = ios->layout->group_width;
u32 U = stripe_unit * group_width;

u32 LmodU;
u64 N = div_u64_rem(file_offset, U, &LmodU);

*unit_off = stripe_mod % stripe_unit;
*obj_offset = stripe_no * stripe_unit + *unit_off;
*dev = stripe_mod / stripe_unit * ios->layout->mirrors_p1;
si->unit_off = LmodU % stripe_unit;
si->obj_offset = N * stripe_unit + si->unit_off;
si->dev = LmodU / stripe_unit;
si->dev *= ios->layout->mirrors_p1;
}

static int _add_stripe_unit(struct exofs_io_state *ios, unsigned *cur_pg,
Expand Down Expand Up @@ -327,65 +345,88 @@ static int _add_stripe_unit(struct exofs_io_state *ios, unsigned *cur_pg,
return 0;
}

static int _prepare_for_striping(struct exofs_io_state *ios)
static int _prepare_pages(struct exofs_io_state *ios,
struct _striping_info *si)
{
u64 length = ios->length;
u64 offset = ios->offset;
unsigned stripe_unit = ios->layout->stripe_unit;
unsigned mirrors_p1 = ios->layout->mirrors_p1;
unsigned dev = si->dev;
unsigned comp = 0;
unsigned stripes = 0;
unsigned cur_pg = 0;
int ret = 0;

if (!ios->pages) {
if (ios->kern_buff) {
struct exofs_per_dev_state *per_dev = &ios->per_dev[0];
unsigned unit_off;

_offset_dev_unit_off(ios, offset, &per_dev->offset,
&per_dev->dev, &unit_off);
/* no cross device without page array */
BUG_ON((ios->layout->group_width > 1) &&
(unit_off + length > stripe_unit));
}
ios->numdevs = ios->layout->mirrors_p1;
return 0;
}

while (length) {
struct exofs_per_dev_state *per_dev = &ios->per_dev[comp];
unsigned cur_len, page_off;
unsigned cur_len, page_off = 0;

if (!per_dev->length) {
unsigned unit_off;
per_dev->dev = dev;
if (dev < si->dev) {
per_dev->offset = si->obj_offset + stripe_unit -
si->unit_off;
cur_len = stripe_unit;
} else if (dev == si->dev) {
per_dev->offset = si->obj_offset;
cur_len = stripe_unit - si->unit_off;
page_off = si->unit_off & ~PAGE_MASK;
BUG_ON(page_off && (page_off != ios->pgbase));
} else { /* dev > si->dev */
per_dev->offset = si->obj_offset - si->unit_off;
cur_len = stripe_unit;
}

_offset_dev_unit_off(ios, offset, &per_dev->offset,
&per_dev->dev, &unit_off);
stripes++;
cur_len = min_t(u64, stripe_unit - unit_off, length);
offset += cur_len;
page_off = unit_off & ~PAGE_MASK;
BUG_ON(page_off != ios->pgbase);

dev += mirrors_p1;
dev %= ios->layout->s_numdevs;
} else {
cur_len = min_t(u64, stripe_unit, length);
page_off = 0;
cur_len = stripe_unit;
}
if (cur_len >= length)
cur_len = length;

ret = _add_stripe_unit(ios, &cur_pg, page_off , per_dev,
cur_len);
if (unlikely(ret))
goto out;

comp += ios->layout->mirrors_p1;
comp += mirrors_p1;
comp %= ios->layout->s_numdevs;

length -= cur_len;
}
out:
ios->numdevs = stripes * ios->layout->mirrors_p1;
ios->numdevs = stripes * mirrors_p1;
return ret;
}

static int _prepare_for_striping(struct exofs_io_state *ios)
{
struct _striping_info si;

_calc_stripe_info(ios, ios->offset, &si);

if (!ios->pages) {
if (ios->kern_buff) {
struct exofs_per_dev_state *per_dev = &ios->per_dev[0];

per_dev->offset = si.obj_offset;
per_dev->dev = si.dev;

/* no cross device without page array */
BUG_ON((ios->layout->group_width > 1) &&
(si.unit_off + ios->length >
ios->layout->stripe_unit));
}
ios->numdevs = ios->layout->mirrors_p1;
return 0;
}

return _prepare_pages(ios, &si);
}

int exofs_sbi_create(struct exofs_io_state *ios)
{
int i, ret;
Expand Down Expand Up @@ -648,9 +689,7 @@ int exofs_oi_truncate(struct exofs_i_info *oi, u64 size)
struct osd_attr attr;
__be64 newsize;
} *size_attrs;
u64 this_obj_size;
unsigned dev;
unsigned unit_off;
struct _striping_info si;
int i, ret;

ret = exofs_get_io_state(&sbi->layout, &ios);
Expand All @@ -668,19 +707,19 @@ int exofs_oi_truncate(struct exofs_i_info *oi, u64 size)
ios->cred = oi->i_cred;

ios->numdevs = ios->layout->s_numdevs;
_offset_dev_unit_off(ios, size, &this_obj_size, &dev, &unit_off);
_calc_stripe_info(ios, size, &si);

for (i = 0; i < ios->layout->group_width; ++i) {
struct exofs_trunc_attr *size_attr = &size_attrs[i];
u64 obj_size;

if (i < dev)
obj_size = this_obj_size +
ios->layout->stripe_unit - unit_off;
else if (i == dev)
obj_size = this_obj_size;
else /* i > dev */
obj_size = this_obj_size - unit_off;
if (i < si.dev)
obj_size = si.obj_offset +
ios->layout->stripe_unit - si.unit_off;
else if (i == si.dev)
obj_size = si.obj_offset;
else /* i > si.dev */
obj_size = si.obj_offset - si.unit_off;

size_attr->newsize = cpu_to_be64(obj_size);
size_attr->attr = g_attr_logical_length;
Expand Down

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