dm bufio: add sector start offset to dm-bufio interface

Introduce dm_bufio_set_sector_offset() interface to allow setting a
sector offset for a dm-bufio client.  This is a prereq for the DM
integrity target.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Milan Broz <gmazyland@gmail.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

2 files changed, 39 insertions, 19 deletions

diff --git a/drivers/md/dm-bufio.c b/drivers/md/dm-bufio.c
index df4859f6ac6a..280b56c229d6 100644
--- a/drivers/md/dm-bufio.c
+++ b/drivers/md/dm-bufio.c
@@ -110,6 +110,8 @@ struct dm_bufio_client {
         struct rb_root buffer_tree;
         wait_queue_head_t free_buffer_wait;
 
+        sector_t start;
+
         int async_write_error;
 
         struct list_head client_list;
@@ -557,8 +559,8 @@ static void dmio_complete(unsigned long error, void *context)
         b->bio.bi_end_io(&b->bio);
 }
 
-static void use_dmio(struct dm_buffer *b, int rw, sector_t block,
-                     bio_end_io_t *end_io)
+static void use_dmio(struct dm_buffer *b, int rw, sector_t sector,
+                     unsigned n_sectors, bio_end_io_t *end_io)
 {
         int r;
         struct dm_io_request io_req = {
@@ -570,8 +572,8 @@ static void use_dmio(struct dm_buffer *b, int rw, sector_t block,
         };
         struct dm_io_region region = {
                 .bdev = b->c->bdev,
-                .sector = block << b->c->sectors_per_block_bits,
-                .count = b->c->block_size >> SECTOR_SHIFT,
+                .sector = sector,
+                .count = n_sectors,
         };
 
         if (b->data_mode != DATA_MODE_VMALLOC) {
@@ -606,14 +608,14 @@ static void inline_endio(struct bio *bio)
         end_fn(bio);
 }
 
-static void use_inline_bio(struct dm_buffer *b, int rw, sector_t block,
-                           bio_end_io_t *end_io)
+static void use_inline_bio(struct dm_buffer *b, int rw, sector_t sector,
+                           unsigned n_sectors, bio_end_io_t *end_io)
 {
         char *ptr;
         int len;
 
         bio_init(&b->bio, b->bio_vec, DM_BUFIO_INLINE_VECS);
-        b->bio.bi_iter.bi_sector = block << b->c->sectors_per_block_bits;
+        b->bio.bi_iter.bi_sector = sector;
         b->bio.bi_bdev = b->c->bdev;
         b->bio.bi_end_io = inline_endio;
         /*
@@ -628,7 +630,7 @@ static void use_inline_bio(struct dm_buffer *b, int rw, sector_t block,
          * If len < PAGE_SIZE the buffer doesn't cross page boundary.
          */
         ptr = b->data;
-        len = b->c->block_size;
+        len = n_sectors << SECTOR_SHIFT;
 
         if (len >= PAGE_SIZE)
                 BUG_ON((unsigned long)ptr & (PAGE_SIZE - 1));
@@ -640,7 +642,7 @@ static void use_inline_bio(struct dm_buffer *b, int rw, sector_t block,
                                   len < PAGE_SIZE ? len : PAGE_SIZE,
                                   offset_in_page(ptr))) {
                         BUG_ON(b->c->block_size <= PAGE_SIZE);
-                        use_dmio(b, rw, block, end_io);
+                        use_dmio(b, rw, sector, n_sectors, end_io);
                         return;
                 }
 
@@ -651,17 +653,22 @@ static void use_inline_bio(struct dm_buffer *b, int rw, sector_t block,
         submit_bio(&b->bio);
 }
 
-static void submit_io(struct dm_buffer *b, int rw, sector_t block,
-                      bio_end_io_t *end_io)
+static void submit_io(struct dm_buffer *b, int rw, bio_end_io_t *end_io)
 {
+        unsigned n_sectors;
+        sector_t sector;
+
         if (rw == WRITE && b->c->write_callback)
                 b->c->write_callback(b);
 
-        if (b->c->block_size <= DM_BUFIO_INLINE_VECS * PAGE_SIZE &&
+        sector = (b->block << b->c->sectors_per_block_bits) + b->c->start;
+        n_sectors = 1 << b->c->sectors_per_block_bits;
+
+        if (n_sectors <= ((DM_BUFIO_INLINE_VECS * PAGE_SIZE) >> SECTOR_SHIFT) &&
             b->data_mode != DATA_MODE_VMALLOC)
-                use_inline_bio(b, rw, block, end_io);
+                use_inline_bio(b, rw, sector, n_sectors, end_io);
         else
-                use_dmio(b, rw, block, end_io);
+                use_dmio(b, rw, sector, n_sectors, end_io);
 }
 
 /*----------------------------------------------------------------
@@ -713,7 +720,7 @@ static void __write_dirty_buffer(struct dm_buffer *b,
         wait_on_bit_lock_io(&b->state, B_WRITING, TASK_UNINTERRUPTIBLE);
 
         if (!write_list)
-                submit_io(b, WRITE, b->block, write_endio);
+                submit_io(b, WRITE, write_endio);
         else
                 list_add_tail(&b->write_list, write_list);
 }
@@ -726,7 +733,7 @@ static void __flush_write_list(struct list_head *write_list)
                 struct dm_buffer *b =
                         list_entry(write_list->next, struct dm_buffer, write_list);
                 list_del(&b->write_list);
-                submit_io(b, WRITE, b->block, write_endio);
+                submit_io(b, WRITE, write_endio);
                 cond_resched();
         }
         blk_finish_plug(&plug);
@@ -1094,7 +1101,7 @@ static void *new_read(struct dm_bufio_client *c, sector_t block,
                 return NULL;
 
         if (need_submit)
-                submit_io(b, READ, b->block, read_endio);
+                submit_io(b, READ, read_endio);
 
         wait_on_bit_io(&b->state, B_READING, TASK_UNINTERRUPTIBLE);
 
@@ -1164,7 +1171,7 @@ void dm_bufio_prefetch(struct dm_bufio_client *c,
                         dm_bufio_unlock(c);
 
                         if (need_submit)
-                                submit_io(b, READ, b->block, read_endio);
+                                submit_io(b, READ, read_endio);
                         dm_bufio_release(b);
 
                         cond_resched();
@@ -1405,7 +1412,7 @@ retry:
                 old_block = b->block;
                 __unlink_buffer(b);
                 __link_buffer(b, new_block, b->list_mode);
-                submit_io(b, WRITE, new_block, write_endio);
+                submit_io(b, WRITE, write_endio);
                 wait_on_bit_io(&b->state, B_WRITING,
                                TASK_UNINTERRUPTIBLE);
                 __unlink_buffer(b);
@@ -1762,6 +1769,12 @@ void dm_bufio_client_destroy(struct dm_bufio_client *c)
 }
 EXPORT_SYMBOL_GPL(dm_bufio_client_destroy);
 
+void dm_bufio_set_sector_offset(struct dm_bufio_client *c, sector_t start)
+{
+        c->start = start;
+}
+EXPORT_SYMBOL_GPL(dm_bufio_set_sector_offset);
+
 static unsigned get_max_age_hz(void)
 {
         unsigned max_age = ACCESS_ONCE(dm_bufio_max_age);
diff --git a/drivers/md/dm-bufio.h b/drivers/md/dm-bufio.h
index c096779a7292..b6d8f53ec15b 100644
--- a/drivers/md/dm-bufio.h
+++ b/drivers/md/dm-bufio.h
@@ -32,6 +32,13 @@ dm_bufio_client_create(struct block_device *bdev, unsigned block_size,
 void dm_bufio_client_destroy(struct dm_bufio_client *c);
 
 /*
+ * Set the sector range.
+ * When this function is called, there must be no I/O in progress on the bufio
+ * client.
+ */
+void dm_bufio_set_sector_offset(struct dm_bufio_client *c, sector_t start);
+
+/*
  * WARNING: to avoid deadlocks, these conditions are observed:
  *
  * - At most one thread can hold at most "reserved_buffers" simultaneously.