btrfs: split page locking out of __process_pages_contig

There is a lot of complexity in __process_pages_contig to deal with the
PAGE_LOCK case that can return an error unlike all the other actions.

Open code the page iteration for page locking in lock_delalloc_pages and
remove all the now unused code from __process_pages_contig.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 662d991..7925c8b 100644 (file)
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -197,18 +197,9 @@ void extent_range_redirty_for_io(struct inode *inode, u64 start, u64 end)
        }
 }
 
-/*
- * Process one page for __process_pages_contig().
- *
- * Return >0 if we hit @page == @locked_page.
- * Return 0 if we updated the page status.
- * Return -EGAIN if the we need to try again.
- * (For PAGE_LOCK case but got dirty page or page not belong to mapping)
- */
-static int process_one_page(struct btrfs_fs_info *fs_info,
-                           struct address_space *mapping,
-                           struct page *page, struct page *locked_page,
-                           unsigned long page_ops, u64 start, u64 end)
+static void process_one_page(struct btrfs_fs_info *fs_info,
+                            struct page *page, struct page *locked_page,
+                            unsigned long page_ops, u64 start, u64 end)
 {
        u32 len;
 
@@ -224,94 +215,36 @@ static int process_one_page(struct btrfs_fs_info *fs_info,
        if (page_ops & PAGE_END_WRITEBACK)
                btrfs_page_clamp_clear_writeback(fs_info, page, start, len);
 
-       if (page == locked_page)
-               return 1;
-
-       if (page_ops & PAGE_LOCK) {
-               int ret;
-
-               ret = btrfs_page_start_writer_lock(fs_info, page, start, len);
-               if (ret)
-                       return ret;
-               if (!PageDirty(page) || page->mapping != mapping) {
-                       btrfs_page_end_writer_lock(fs_info, page, start, len);
-                       return -EAGAIN;
-               }
-       }
-       if (page_ops & PAGE_UNLOCK)
+       if (page != locked_page && (page_ops & PAGE_UNLOCK))
                btrfs_page_end_writer_lock(fs_info, page, start, len);
-       return 0;
 }
 
-static int __process_pages_contig(struct address_space *mapping,
-                                 struct page *locked_page,
-                                 u64 start, u64 end, unsigned long page_ops,
-                                 u64 *processed_end)
+static void __process_pages_contig(struct address_space *mapping,
+                                  struct page *locked_page, u64 start, u64 end,
+                                  unsigned long page_ops)
 {
        struct btrfs_fs_info *fs_info = btrfs_sb(mapping->host->i_sb);
        pgoff_t start_index = start >> PAGE_SHIFT;
        pgoff_t end_index = end >> PAGE_SHIFT;
        pgoff_t index = start_index;
-       unsigned long pages_processed = 0;
        struct folio_batch fbatch;
-       int err = 0;
        int i;
 
-       if (page_ops & PAGE_LOCK) {
-               ASSERT(page_ops == PAGE_LOCK);
-               ASSERT(processed_end && *processed_end == start);
-       }
-
        folio_batch_init(&fbatch);
        while (index <= end_index) {
                int found_folios;
 
                found_folios = filemap_get_folios_contig(mapping, &index,
                                end_index, &fbatch);
-
-               if (found_folios == 0) {
-                       /*
-                        * Only if we're going to lock these pages, we can find
-                        * nothing at @index.
-                        */
-                       ASSERT(page_ops & PAGE_LOCK);
-                       err = -EAGAIN;
-                       goto out;
-               }
-
                for (i = 0; i < found_folios; i++) {
-                       int process_ret;
                        struct folio *folio = fbatch.folios[i];
-                       process_ret = process_one_page(fs_info, mapping,
-                                       &folio->page, locked_page, page_ops,
-                                       start, end);
-                       if (process_ret < 0) {
-                               err = -EAGAIN;
-                               folio_batch_release(&fbatch);
-                               goto out;
-                       }
-                       pages_processed += folio_nr_pages(folio);
+
+                       process_one_page(fs_info, &folio->page, locked_page,
+                                        page_ops, start, end);
                }
                folio_batch_release(&fbatch);
                cond_resched();
        }
-out:
-       if (err && processed_end) {
-               /*
-                * Update @processed_end. I know this is awful since it has
-                * two different return value patterns (inclusive vs exclusive).
-                *
-                * But the exclusive pattern is necessary if @start is 0, or we
-                * underflow and check against processed_end won't work as
-                * expected.
-                */
-               if (pages_processed)
-                       *processed_end = min(end,
-                       ((u64)(start_index + pages_processed) << PAGE_SHIFT) - 1);
-               else
-                       *processed_end = start;
-       }
-       return err;
 }
 
 static noinline void __unlock_for_delalloc(struct inode *inode,
@@ -326,29 +259,63 @@ static noinline void __unlock_for_delalloc(struct inode *inode,
                return;
 
        __process_pages_contig(inode->i_mapping, locked_page, start, end,
-                              PAGE_UNLOCK, NULL);
+                              PAGE_UNLOCK);
 }
 
 static noinline int lock_delalloc_pages(struct inode *inode,
                                        struct page *locked_page,
-                                       u64 delalloc_start,
-                                       u64 delalloc_end)
+                                       u64 start,
+                                       u64 end)
 {
-       unsigned long index = delalloc_start >> PAGE_SHIFT;
-       unsigned long end_index = delalloc_end >> PAGE_SHIFT;
-       u64 processed_end = delalloc_start;
-       int ret;
+       struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
+       struct address_space *mapping = inode->i_mapping;
+       pgoff_t start_index = start >> PAGE_SHIFT;
+       pgoff_t end_index = end >> PAGE_SHIFT;
+       pgoff_t index = start_index;
+       u64 processed_end = start;
+       struct folio_batch fbatch;
 
-       ASSERT(locked_page);
        if (index == locked_page->index && index == end_index)
                return 0;
 
-       ret = __process_pages_contig(inode->i_mapping, locked_page, delalloc_start,
-                                    delalloc_end, PAGE_LOCK, &processed_end);
-       if (ret == -EAGAIN && processed_end > delalloc_start)
-               __unlock_for_delalloc(inode, locked_page, delalloc_start,
-                                     processed_end);
-       return ret;
+       folio_batch_init(&fbatch);
+       while (index <= end_index) {
+               unsigned int found_folios, i;
+
+               found_folios = filemap_get_folios_contig(mapping, &index,
+                               end_index, &fbatch);
+               if (found_folios == 0)
+                       goto out;
+
+               for (i = 0; i < found_folios; i++) {
+                       struct page *page = &fbatch.folios[i]->page;
+                       u32 len = end + 1 - start;
+
+                       if (page == locked_page)
+                               continue;
+
+                       if (btrfs_page_start_writer_lock(fs_info, page, start,
+                                                        len))
+                               goto out;
+
+                       if (!PageDirty(page) || page->mapping != mapping) {
+                               btrfs_page_end_writer_lock(fs_info, page, start,
+                                                          len);
+                               goto out;
+                       }
+
+                       processed_end = page_offset(page) + PAGE_SIZE - 1;
+               }
+               folio_batch_release(&fbatch);
+               cond_resched();
+       }
+
+       return 0;
+out:
+       folio_batch_release(&fbatch);
+       if (processed_end > start)
+               __unlock_for_delalloc(inode, locked_page, start, processed_end);
+       return -EAGAIN;
 }
 
 /*
@@ -467,7 +434,7 @@ void extent_clear_unlock_delalloc(struct btrfs_inode *inode, u64 start, u64 end,
        clear_extent_bit(&inode->io_tree, start, end, clear_bits, NULL);
 
        __process_pages_contig(inode->vfs_inode.i_mapping, locked_page,
-                              start, end, page_ops, NULL);
+                              start, end, page_ops);
 }
 
 static bool btrfs_verify_page(struct page *page, u64 start)

diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
index c5fae3a..2857541 100644 (file)
--- a/fs/btrfs/extent_io.h
+++ b/fs/btrfs/extent_io.h
@@ -40,7 +40,6 @@ enum {
        ENUM_BIT(PAGE_START_WRITEBACK),
        ENUM_BIT(PAGE_END_WRITEBACK),
        ENUM_BIT(PAGE_SET_ORDERED),
-       ENUM_BIT(PAGE_LOCK),
 };
 
 /*