exofs: convert io_state to use pages array instead of bio at input

* inode.c operations are full-pages based, and not actually
  true scatter-gather
* Lets us use more pages at once upto 512 (from 249) in 64 bit
* Brings us much much closer to be able to use exofs's io_state engine
  from objlayout driver. (Once I decide where to put the common code)

After RAID0 patch the outer (input) bio was never used as a bio, but
was simply a page carrier into the raid engine. Even in the simple
mirror/single-dev arrangement pages info was copied into a second bio.
It is now easer to just pass a pages array into the io_state and prepare
bio(s) once.

Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>

1 files changed, 26 insertions, 20 deletions

diff --git a/fs/exofs/ios.c b/fs/exofs/ios.c
index 6e446b2670b9..263052c77f41 100644
--- a/fs/exofs/ios.c
+++ b/fs/exofs/ios.c
@@ -283,10 +283,11 @@ static void _offset_dev_unit_off(struct exofs_io_state *ios, u64 file_offset,
         *dev = stripe_mod / stripe_unit * ios->layout->mirrors_p1;
 }
 
-static int _add_stripe_unit(struct exofs_io_state *ios,  unsigned *cur_bvec,
-                     struct exofs_per_dev_state *per_dev, int cur_len)
+static int _add_stripe_unit(struct exofs_io_state *ios,  unsigned *cur_pg,
+                unsigned pgbase, struct exofs_per_dev_state *per_dev,
+                int cur_len)
 {
-        unsigned bv = *cur_bvec;
+        unsigned pg = *cur_pg;
         struct request_queue *q =
                         osd_request_queue(exofs_ios_od(ios, per_dev->dev));
 
@@ -295,7 +296,7 @@ static int _add_stripe_unit(struct exofs_io_state *ios,  unsigned *cur_bvec,
         if (per_dev->bio == NULL) {
                 unsigned pages_in_stripe = ios->layout->group_width *
                                         (ios->layout->stripe_unit / PAGE_SIZE);
-                unsigned bio_size = (ios->bio->bi_vcnt + pages_in_stripe) /
+                unsigned bio_size = (ios->nr_pages + pages_in_stripe) /
                                                 ios->layout->group_width;
 
                 per_dev->bio = bio_kmalloc(GFP_KERNEL, bio_size);
@@ -307,21 +308,22 @@ static int _add_stripe_unit(struct exofs_io_state *ios,  unsigned *cur_bvec,
         }
 
         while (cur_len > 0) {
-                int added_len;
-                struct bio_vec *bvec = &ios->bio->bi_io_vec[bv];
+                unsigned pglen = min_t(unsigned, PAGE_SIZE - pgbase, cur_len);
+                unsigned added_len;
 
-                BUG_ON(ios->bio->bi_vcnt <= bv);
-                cur_len -= bvec->bv_len;
+                BUG_ON(ios->nr_pages <= pg);
+                cur_len -= pglen;
 
-                added_len = bio_add_pc_page(q, per_dev->bio, bvec->bv_page,
-                                            bvec->bv_len, bvec->bv_offset);
-                if (unlikely(bvec->bv_len != added_len))
+                added_len = bio_add_pc_page(q, per_dev->bio, ios->pages[pg],
+                                            pglen, pgbase);
+                if (unlikely(pglen != added_len))
                         return -ENOMEM;
-                ++bv;
+                pgbase = 0;
+                ++pg;
         }
         BUG_ON(cur_len);
 
-        *cur_bvec = bv;
+        *cur_pg = pg;
         return 0;
 }
 
@@ -332,10 +334,10 @@ static int _prepare_for_striping(struct exofs_io_state *ios)
         unsigned stripe_unit = ios->layout->stripe_unit;
         unsigned comp = 0;
         unsigned stripes = 0;
-        unsigned cur_bvec = 0;
-        int ret;
+        unsigned cur_pg = 0;
+        int ret = 0;
 
-        if (!ios->bio) {
+        if (!ios->pages) {
                 if (ios->kern_buff) {
                         struct exofs_per_dev_state *per_dev = &ios->per_dev[0];
                         unsigned unit_off;
@@ -352,7 +354,7 @@ static int _prepare_for_striping(struct exofs_io_state *ios)
 
         while (length) {
                 struct exofs_per_dev_state *per_dev = &ios->per_dev[comp];
-                unsigned cur_len;
+                unsigned cur_len, page_off;
 
                 if (!per_dev->length) {
                         unsigned unit_off;
@@ -362,11 +364,15 @@ static int _prepare_for_striping(struct exofs_io_state *ios)
                         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);
                 } else {
                         cur_len = min_t(u64, stripe_unit, length);
+                        page_off = 0;
                 }
 
-                ret = _add_stripe_unit(ios, &cur_bvec, per_dev, cur_len);
+                ret = _add_stripe_unit(ios, &cur_pg, page_off , per_dev,
+                                       cur_len);
                 if (unlikely(ret))
                         goto out;
 
@@ -448,7 +454,7 @@ static int _sbi_write_mirror(struct exofs_io_state *ios, int cur_comp)
                 per_dev->or = or;
                 per_dev->offset = master_dev->offset;
 
-                if (ios->bio) {
+                if (ios->pages) {
                         struct bio *bio;
 
                         if (per_dev != master_dev) {
@@ -541,7 +547,7 @@ static int _sbi_read_mirror(struct exofs_io_state *ios, unsigned cur_comp)
         }
         per_dev->or = or;
 
-        if (ios->bio) {
+        if (ios->pages) {
                 osd_req_read(or, &ios->obj, per_dev->offset,
                                 per_dev->bio, per_dev->length);
                 EXOFS_DBGMSG("read(0x%llx) offset=0x%llx length=0x%llx"