[PATCH] ocfs2 heartbeat: clean up bio submission code

As was already pointed out Mathieu Avila on Thu, 07 Sep 2006 03:15:25 -0700
that OCFS2 is expecting bio_add_page() to add pages to BIOs in an easily
predictable manner.

That is not true, especially for devices with own merge_bvec_fn().

Therefore OCFS2's heartbeat code is very likely to fail on such devices.

Move the bio_put() call into the bio's bi_end_io() function. This makes the
whole idea of trying to predict the behaviour of bio_add_page() unnecessary.
Removed compute_max_sectors() and o2hb_compute_request_limits().

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>

1 files changed, 31 insertions, 127 deletions

diff --git a/fs/ocfs2/cluster/heartbeat.c b/fs/ocfs2/cluster/heartbeat.c
index 277ca67a2ad..5a9779bb923 100644
--- a/fs/ocfs2/cluster/heartbeat.c
+++ b/fs/ocfs2/cluster/heartbeat.c
@@ -184,10 +184,9 @@ static void o2hb_disarm_write_timeout(struct o2hb_region *reg)
         flush_scheduled_work();
 }
 
-static inline void o2hb_bio_wait_init(struct o2hb_bio_wait_ctxt *wc,
-                                      unsigned int num_ios)
+static inline void o2hb_bio_wait_init(struct o2hb_bio_wait_ctxt *wc)
 {
-        atomic_set(&wc->wc_num_reqs, num_ios);
+        atomic_set(&wc->wc_num_reqs, 1);
         init_completion(&wc->wc_io_complete);
         wc->wc_error = 0;
 }
@@ -212,6 +211,7 @@ static void o2hb_wait_on_io(struct o2hb_region *reg,
         struct address_space *mapping = reg->hr_bdev->bd_inode->i_mapping;
 
         blk_run_address_space(mapping);
+        o2hb_bio_wait_dec(wc, 1);
 
         wait_for_completion(&wc->wc_io_complete);
 }
@@ -231,6 +231,7 @@ static int o2hb_bio_end_io(struct bio *bio,
                 return 1;
 
         o2hb_bio_wait_dec(wc, 1);
+        bio_put(bio);
         return 0;
 }
 
@@ -238,23 +239,22 @@ static int o2hb_bio_end_io(struct bio *bio,
  * start_slot. */
 static struct bio *o2hb_setup_one_bio(struct o2hb_region *reg,
                                       struct o2hb_bio_wait_ctxt *wc,
-                                      unsigned int start_slot,
-                                      unsigned int num_slots)
+                                      unsigned int *current_slot,
+                                      unsigned int max_slots)
 {
-        int i, nr_vecs, len, first_page, last_page;
+        int len, current_page;
         unsigned int vec_len, vec_start;
         unsigned int bits = reg->hr_block_bits;
         unsigned int spp = reg->hr_slots_per_page;
+        unsigned int cs = *current_slot;
         struct bio *bio;
         struct page *page;
 
-        nr_vecs = (num_slots + spp - 1) / spp;
-
         /* Testing has shown this allocation to take long enough under
          * GFP_KERNEL that the local node can get fenced. It would be
          * nicest if we could pre-allocate these bios and avoid this
          * all together. */
-        bio = bio_alloc(GFP_ATOMIC, nr_vecs);
+        bio = bio_alloc(GFP_ATOMIC, 16);
         if (!bio) {
                 mlog(ML_ERROR, "Could not alloc slots BIO!\n");
                 bio = ERR_PTR(-ENOMEM);
@@ -262,137 +262,53 @@ static struct bio *o2hb_setup_one_bio(struct o2hb_region *reg,
         }
 
         /* Must put everything in 512 byte sectors for the bio... */
-        bio->bi_sector = (reg->hr_start_block + start_slot) << (bits - 9);
+        bio->bi_sector = (reg->hr_start_block + cs) << (bits - 9);
         bio->bi_bdev = reg->hr_bdev;
         bio->bi_private = wc;
         bio->bi_end_io = o2hb_bio_end_io;
 
-        first_page = start_slot / spp;
-        last_page = first_page + nr_vecs;
-        vec_start = (start_slot << bits) % PAGE_CACHE_SIZE;
-        for(i = first_page; i < last_page; i++) {
-                page = reg->hr_slot_data[i];
+        vec_start = (cs << bits) % PAGE_CACHE_SIZE;
+        while(cs < max_slots) {
+                current_page = cs / spp;
+                page = reg->hr_slot_data[current_page];
 
-                vec_len = PAGE_CACHE_SIZE;
-                /* last page might be short */
-                if (((i + 1) * spp) > (start_slot + num_slots))
-                        vec_len = ((num_slots + start_slot) % spp) << bits;
-                vec_len -=  vec_start;
+                vec_len = min(PAGE_CACHE_SIZE,
+                              (max_slots-cs) * (PAGE_CACHE_SIZE/spp) );
 
                 mlog(ML_HB_BIO, "page %d, vec_len = %u, vec_start = %u\n",
-                     i, vec_len, vec_start);
+                     current_page, vec_len, vec_start);
 
                 len = bio_add_page(bio, page, vec_len, vec_start);
-                if (len != vec_len) {
-                        bio_put(bio);
-                        bio = ERR_PTR(-EIO);
-
-                        mlog(ML_ERROR, "Error adding page to bio i = %d, "
-                             "vec_len = %u, len = %d\n, start = %u\n",
-                             i, vec_len, len, vec_start);
-                        goto bail;
-                }
+                if (len != vec_len) break;
 
+                cs += vec_len / (PAGE_CACHE_SIZE/spp);
                 vec_start = 0;
         }
 
 bail:
+        *current_slot = cs;
         return bio;
 }
 
-/*
- * Compute the maximum number of sectors the bdev can handle in one bio,
- * as a power of two.
- *
- * Stolen from oracleasm, thanks Joel!
- */
-static int compute_max_sectors(struct block_device *bdev)
-{
-        int max_pages, max_sectors, pow_two_sectors;
-
-        struct request_queue *q;
-
-        q = bdev_get_queue(bdev);
-        max_pages = q->max_sectors >> (PAGE_SHIFT - 9);
-        if (max_pages > BIO_MAX_PAGES)
-                max_pages = BIO_MAX_PAGES;
-        if (max_pages > q->max_phys_segments)
-                max_pages = q->max_phys_segments;
-        if (max_pages > q->max_hw_segments)
-                max_pages = q->max_hw_segments;
-        max_pages--; /* Handle I/Os that straddle a page */
-
-        if (max_pages) {
-                max_sectors = max_pages << (PAGE_SHIFT - 9);
-        } else {
-                /* If BIO contains 1 or less than 1 page. */
-                max_sectors = q->max_sectors;
-        }
-        /* Why is fls() 1-based???? */
-        pow_two_sectors = 1 << (fls(max_sectors) - 1);
-
-        return pow_two_sectors;
-}
-
-static inline void o2hb_compute_request_limits(struct o2hb_region *reg,
-                                               unsigned int num_slots,
-                                               unsigned int *num_bios,
-                                               unsigned int *slots_per_bio)
-{
-        unsigned int max_sectors, io_sectors;
-
-        max_sectors = compute_max_sectors(reg->hr_bdev);
-
-        io_sectors = num_slots << (reg->hr_block_bits - 9);
-
-        *num_bios = (io_sectors + max_sectors - 1) / max_sectors;
-        *slots_per_bio = max_sectors >> (reg->hr_block_bits - 9);
-
-        mlog(ML_HB_BIO, "My io size is %u sectors for %u slots. This "
-             "device can handle %u sectors of I/O\n", io_sectors, num_slots,
-             max_sectors);
-        mlog(ML_HB_BIO, "Will need %u bios holding %u slots each\n",
-             *num_bios, *slots_per_bio);
-}
-
 static int o2hb_read_slots(struct o2hb_region *reg,
                            unsigned int max_slots)
 {
-        unsigned int num_bios, slots_per_bio, start_slot, num_slots;
-        int i, status;
+        unsigned int current_slot=0;
+        int status;
         struct o2hb_bio_wait_ctxt wc;
-        struct bio **bios;
         struct bio *bio;
 
-        o2hb_compute_request_limits(reg, max_slots, &num_bios, &slots_per_bio);
+        o2hb_bio_wait_init(&wc);
 
-        bios = kcalloc(num_bios, sizeof(struct bio *), GFP_KERNEL);
-        if (!bios) {
-                status = -ENOMEM;
-                mlog_errno(status);
-                return status;
-        }
-
-        o2hb_bio_wait_init(&wc, num_bios);
-
-        num_slots = slots_per_bio;
-        for(i = 0; i < num_bios; i++) {
-                start_slot = i * slots_per_bio;
-
-                /* adjust num_slots at last bio */
-                if (max_slots < (start_slot + num_slots))
-                        num_slots = max_slots - start_slot;
-
-                bio = o2hb_setup_one_bio(reg, &wc, start_slot, num_slots);
+        while(current_slot < max_slots) {
+                bio = o2hb_setup_one_bio(reg, &wc, &current_slot, max_slots);
                 if (IS_ERR(bio)) {
-                        o2hb_bio_wait_dec(&wc, num_bios - i);
-
                         status = PTR_ERR(bio);
                         mlog_errno(status);
                         goto bail_and_wait;
                 }
-                bios[i] = bio;
 
+                atomic_inc(&wc.wc_num_reqs);
                 submit_bio(READ, bio);
         }
 
@@ -403,38 +319,30 @@ bail_and_wait:
         if (wc.wc_error && !status)
                 status = wc.wc_error;
 
-        if (bios) {
-                for(i = 0; i < num_bios; i++)
-                        if (bios[i])
-                                bio_put(bios[i]);
-                kfree(bios);
-        }
-
         return status;
 }
 
 static int o2hb_issue_node_write(struct o2hb_region *reg,
-                                 struct bio **write_bio,
                                  struct o2hb_bio_wait_ctxt *write_wc)
 {
         int status;
         unsigned int slot;
         struct bio *bio;
 
-        o2hb_bio_wait_init(write_wc, 1);
+        o2hb_bio_wait_init(write_wc);
 
         slot = o2nm_this_node();
 
-        bio = o2hb_setup_one_bio(reg, write_wc, slot, 1);
+        bio = o2hb_setup_one_bio(reg, write_wc, &slot, slot+1);
         if (IS_ERR(bio)) {
                 status = PTR_ERR(bio);
                 mlog_errno(status);
                 goto bail;
         }
 
+        atomic_inc(&write_wc->wc_num_reqs);
         submit_bio(WRITE, bio);
 
-        *write_bio = bio;
         status = 0;
 bail:
         return status;
@@ -826,7 +734,6 @@ static int o2hb_do_disk_heartbeat(struct o2hb_region *reg)
 {
         int i, ret, highest_node, change = 0;
         unsigned long configured_nodes[BITS_TO_LONGS(O2NM_MAX_NODES)];
-        struct bio *write_bio;
         struct o2hb_bio_wait_ctxt write_wc;
 
         ret = o2nm_configured_node_map(configured_nodes,
@@ -864,7 +771,7 @@ static int o2hb_do_disk_heartbeat(struct o2hb_region *reg)
 
         /* And fire off the write. Note that we don't wait on this I/O
          * until later. */
-        ret = o2hb_issue_node_write(reg, &write_bio, &write_wc);
+        ret = o2hb_issue_node_write(reg, &write_wc);
         if (ret < 0) {
                 mlog_errno(ret);
                 return ret;
@@ -882,7 +789,6 @@ static int o2hb_do_disk_heartbeat(struct o2hb_region *reg)
          * people we find in our steady state have seen us.
          */
         o2hb_wait_on_io(reg, &write_wc);
-        bio_put(write_bio);
         if (write_wc.wc_error) {
                 /* Do not re-arm the write timeout on I/O error - we
                  * can't be sure that the new block ever made it to
@@ -943,7 +849,6 @@ static int o2hb_thread(void *data)
 {
         int i, ret;
         struct o2hb_region *reg = data;
-        struct bio *write_bio;
         struct o2hb_bio_wait_ctxt write_wc;
         struct timeval before_hb, after_hb;
         unsigned int elapsed_msec;
@@ -993,10 +898,9 @@ static int o2hb_thread(void *data)
          *
          * XXX: Should we skip this on unclean_stop? */
         o2hb_prepare_block(reg, 0);
-        ret = o2hb_issue_node_write(reg, &write_bio, &write_wc);
+        ret = o2hb_issue_node_write(reg, &write_wc);
         if (ret == 0) {
                 o2hb_wait_on_io(reg, &write_wc);
-                bio_put(write_bio);
         } else {
                 mlog_errno(ret);
         }