fs: export inode_to_bdi and use it in favor of mapping->backing_dev_info

Now that we got rid of the bdi abuse on character devices we can always use
sb->s_bdi to get at the backing_dev_info for a file, except for the block
device special case.  Export inode_to_bdi and replace uses of
mapping->backing_dev_info with it to prepare for the removal of
mapping->backing_dev_info.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Jens Axboe <axboe@fb.com>

7 files changed, 24 insertions, 26 deletions

diff --git a/mm/fadvise.c b/mm/fadvise.c
index 2ad7adf4f0a4..fac23ecf8d72 100644
--- a/mm/fadvise.c
+++ b/mm/fadvise.c
@@ -73,7 +73,7 @@ SYSCALL_DEFINE4(fadvise64_64, int, fd, loff_t, offset, loff_t, len, int, advice)
         else
                 endbyte--;              /* inclusive */
 
-        bdi = mapping->backing_dev_info;
+        bdi = inode_to_bdi(mapping->host);
 
         switch (advice) {
         case POSIX_FADV_NORMAL:
@@ -113,7 +113,7 @@ SYSCALL_DEFINE4(fadvise64_64, int, fd, loff_t, offset, loff_t, len, int, advice)
         case POSIX_FADV_NOREUSE:
                 break;
         case POSIX_FADV_DONTNEED:
-                if (!bdi_write_congested(mapping->backing_dev_info))
+                if (!bdi_write_congested(bdi))
                         __filemap_fdatawrite_range(mapping, offset, endbyte,
                                                    WB_SYNC_NONE);
 
diff --git a/mm/filemap.c b/mm/filemap.c
index 673e4581a2e5..5d7c23c26f81 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -211,7 +211,7 @@ void __delete_from_page_cache(struct page *page, void *shadow)
          */
         if (PageDirty(page) && mapping_cap_account_dirty(mapping)) {
                 dec_zone_page_state(page, NR_FILE_DIRTY);
-                dec_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE);
+                dec_bdi_stat(inode_to_bdi(mapping->host), BDI_RECLAIMABLE);
         }
 }
 
@@ -2565,7 +2565,7 @@ ssize_t __generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
         size_t          count = iov_iter_count(from);
 
         /* We can write back this queue in page reclaim */
-        current->backing_dev_info = mapping->backing_dev_info;
+        current->backing_dev_info = inode_to_bdi(inode);
         err = generic_write_checks(file, &pos, &count, S_ISBLK(inode->i_mode));
         if (err)
                 goto out;
diff --git a/mm/filemap_xip.c b/mm/filemap_xip.c
index 0d105aeff82f..26897fbfbe19 100644
--- a/mm/filemap_xip.c
+++ b/mm/filemap_xip.c
@@ -9,6 +9,7 @@
  */
 
 #include <linux/fs.h>
+#include <linux/backing-dev.h>
 #include <linux/pagemap.h>
 #include <linux/export.h>
 #include <linux/uio.h>
@@ -410,7 +411,7 @@ xip_file_write(struct file *filp, const char __user *buf, size_t len,
         count = len;
 
         /* We can write back this queue in page reclaim */
-        current->backing_dev_info = mapping->backing_dev_info;
+        current->backing_dev_info = inode_to_bdi(inode);
 
         ret = generic_write_checks(filp, &pos, &count, S_ISBLK(inode->i_mode));
         if (ret)
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 6f4335238e33..d4cbb4bd7d1c 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -1351,7 +1351,7 @@ static void balance_dirty_pages(struct address_space *mapping,
         unsigned long task_ratelimit;
         unsigned long dirty_ratelimit;
         unsigned long pos_ratio;
-        struct backing_dev_info *bdi = mapping->backing_dev_info;
+        struct backing_dev_info *bdi = inode_to_bdi(mapping->host);
         bool strictlimit = bdi->capabilities & BDI_CAP_STRICTLIMIT;
         unsigned long start_time = jiffies;
 
@@ -1574,7 +1574,7 @@ DEFINE_PER_CPU(int, dirty_throttle_leaks) = 0;
  */
 void balance_dirty_pages_ratelimited(struct address_space *mapping)
 {
-        struct backing_dev_info *bdi = mapping->backing_dev_info;
+        struct backing_dev_info *bdi = inode_to_bdi(mapping->host);
         int ratelimit;
         int *p;
 
@@ -1929,7 +1929,7 @@ continue_unlock:
                         if (!clear_page_dirty_for_io(page))
                                 goto continue_unlock;
 
-                        trace_wbc_writepage(wbc, mapping->backing_dev_info);
+                        trace_wbc_writepage(wbc, inode_to_bdi(mapping->host));
                         ret = (*writepage)(page, wbc, data);
                         if (unlikely(ret)) {
                                 if (ret == AOP_WRITEPAGE_ACTIVATE) {
@@ -2094,10 +2094,12 @@ void account_page_dirtied(struct page *page, struct address_space *mapping)
         trace_writeback_dirty_page(page, mapping);
 
         if (mapping_cap_account_dirty(mapping)) {
+                struct backing_dev_info *bdi = inode_to_bdi(mapping->host);
+
                 __inc_zone_page_state(page, NR_FILE_DIRTY);
                 __inc_zone_page_state(page, NR_DIRTIED);
-                __inc_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE);
-                __inc_bdi_stat(mapping->backing_dev_info, BDI_DIRTIED);
+                __inc_bdi_stat(bdi, BDI_RECLAIMABLE);
+                __inc_bdi_stat(bdi, BDI_DIRTIED);
                 task_io_account_write(PAGE_CACHE_SIZE);
                 current->nr_dirtied++;
                 this_cpu_inc(bdp_ratelimits);
@@ -2156,7 +2158,7 @@ void account_page_redirty(struct page *page)
         if (mapping && mapping_cap_account_dirty(mapping)) {
                 current->nr_dirtied--;
                 dec_zone_page_state(page, NR_DIRTIED);
-                dec_bdi_stat(mapping->backing_dev_info, BDI_DIRTIED);
+                dec_bdi_stat(inode_to_bdi(mapping->host), BDI_DIRTIED);
         }
 }
 EXPORT_SYMBOL(account_page_redirty);
@@ -2295,7 +2297,7 @@ int clear_page_dirty_for_io(struct page *page)
                  */
                 if (TestClearPageDirty(page)) {
                         dec_zone_page_state(page, NR_FILE_DIRTY);
-                        dec_bdi_stat(mapping->backing_dev_info,
+                        dec_bdi_stat(inode_to_bdi(mapping->host),
                                         BDI_RECLAIMABLE);
                         return 1;
                 }
@@ -2315,7 +2317,7 @@ int test_clear_page_writeback(struct page *page)
 
         memcg = mem_cgroup_begin_page_stat(page, &locked, &memcg_flags);
         if (mapping) {
-                struct backing_dev_info *bdi = mapping->backing_dev_info;
+                struct backing_dev_info *bdi = inode_to_bdi(mapping->host);
                 unsigned long flags;
 
                 spin_lock_irqsave(&mapping->tree_lock, flags);
@@ -2352,7 +2354,7 @@ int __test_set_page_writeback(struct page *page, bool keep_write)
 
         memcg = mem_cgroup_begin_page_stat(page, &locked, &memcg_flags);
         if (mapping) {
-                struct backing_dev_info *bdi = mapping->backing_dev_info;
+                struct backing_dev_info *bdi = inode_to_bdi(mapping->host);
                 unsigned long flags;
 
                 spin_lock_irqsave(&mapping->tree_lock, flags);
@@ -2406,12 +2408,7 @@ EXPORT_SYMBOL(mapping_tagged);
  */
 void wait_for_stable_page(struct page *page)
 {
-        struct address_space *mapping = page_mapping(page);
-        struct backing_dev_info *bdi = mapping->backing_dev_info;
-
-        if (!bdi_cap_stable_pages_required(bdi))
-                return;
-
-        wait_on_page_writeback(page);
+        if (bdi_cap_stable_pages_required(inode_to_bdi(page->mapping->host)))
+                wait_on_page_writeback(page);
 }
 EXPORT_SYMBOL_GPL(wait_for_stable_page);
diff --git a/mm/readahead.c b/mm/readahead.c
index 17b9172ec37f..935675844b2e 100644
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -27,7 +27,7 @@
 void
 file_ra_state_init(struct file_ra_state *ra, struct address_space *mapping)
 {
-        ra->ra_pages = mapping->backing_dev_info->ra_pages;
+        ra->ra_pages = inode_to_bdi(mapping->host)->ra_pages;
         ra->prev_pos = -1;
 }
 EXPORT_SYMBOL_GPL(file_ra_state_init);
@@ -541,7 +541,7 @@ page_cache_async_readahead(struct address_space *mapping,
         /*
          * Defer asynchronous read-ahead on IO congestion.
          */
-        if (bdi_read_congested(mapping->backing_dev_info))
+        if (bdi_read_congested(inode_to_bdi(mapping->host)))
                 return;
 
         /* do read-ahead */
diff --git a/mm/truncate.c b/mm/truncate.c
index f1e4d6052369..ddec5a5966d7 100644
--- a/mm/truncate.c
+++ b/mm/truncate.c
@@ -112,7 +112,7 @@ void cancel_dirty_page(struct page *page, unsigned int account_size)
                 struct address_space *mapping = page->mapping;
                 if (mapping && mapping_cap_account_dirty(mapping)) {
                         dec_zone_page_state(page, NR_FILE_DIRTY);
-                        dec_bdi_stat(mapping->backing_dev_info,
+                        dec_bdi_stat(inode_to_bdi(mapping->host),
                                         BDI_RECLAIMABLE);
                         if (account_size)
                                 task_io_account_cancelled_write(account_size);
diff --git a/mm/vmscan.c b/mm/vmscan.c
index ab2505c3ef54..e00a16393f21 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -497,7 +497,7 @@ static pageout_t pageout(struct page *page, struct address_space *mapping,
         }
         if (mapping->a_ops->writepage == NULL)
                 return PAGE_ACTIVATE;
-        if (!may_write_to_queue(mapping->backing_dev_info, sc))
+        if (!may_write_to_queue(inode_to_bdi(mapping->host), sc))
                 return PAGE_KEEP;
 
         if (clear_page_dirty_for_io(page)) {
@@ -876,7 +876,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
                  */
                 mapping = page_mapping(page);
                 if (((dirty || writeback) && mapping &&
-                     bdi_write_congested(mapping->backing_dev_info)) ||
+                     bdi_write_congested(inode_to_bdi(mapping->host))) ||
                     (writeback && PageReclaim(page)))
                         nr_congested++;