For subpage case, we need to allocate new memory for each metadata page. So we need to: - Allow attach_extent_buffer_page() to return int To indicate allocation failure
- Prealloc page->private for alloc_extent_buffer() We don't want to call memory allocation with spinlock hold, so do preallocation before we acquire the spin lock. - Handle subpage and regular case differently in attach_extent_buffer_page() For regular case, just do the usual thing. For subpage case, allocate new memory and update the tree_block bitmap. The bitmap update will be handled by new subpage specific helper, btrfs_subpage_set_tree_block(). Signed-off-by: Qu Wenruo <[email protected]> --- fs/btrfs/extent_io.c | 74 ++++++++++++++++++++++++++++++++++---------- fs/btrfs/subpage.h | 50 ++++++++++++++++++++++++++++++ 2 files changed, 108 insertions(+), 16 deletions(-) diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c index d60f1837f8fb..2eeff925450f 100644 --- a/fs/btrfs/extent_io.c +++ b/fs/btrfs/extent_io.c @@ -24,6 +24,7 @@ #include "rcu-string.h" #include "backref.h" #include "disk-io.h" +#include "subpage.h" static struct kmem_cache *extent_state_cache; static struct kmem_cache *extent_buffer_cache; @@ -3140,22 +3141,41 @@ static int submit_extent_page(unsigned int opf, return ret; } -static void attach_extent_buffer_page(struct extent_buffer *eb, +static int attach_extent_buffer_page(struct extent_buffer *eb, struct page *page) { - /* - * If the page is mapped to btree inode, we should hold the private - * lock to prevent race. - * For cloned or dummy extent buffers, their pages are not mapped and - * will not race with any other ebs. - */ - if (page->mapping) - lockdep_assert_held(&page->mapping->private_lock); + struct btrfs_fs_info *fs_info = eb->fs_info; + int ret; - if (!PagePrivate(page)) - attach_page_private(page, eb); - else - WARN_ON(page->private != (unsigned long)eb); + if (fs_info->sectorsize == PAGE_SIZE) { + /* + * If the page is mapped to btree inode, we should hold the + * private lock to prevent race. + * For cloned or dummy extent buffers, their pages are not + * mapped and will not race with any other ebs. + */ + if (page->mapping) + lockdep_assert_held(&page->mapping->private_lock); + + if (!PagePrivate(page)) + attach_page_private(page, eb); + else + WARN_ON(page->private != (unsigned long)eb); + return 0; + } + + /* Already mapped, just update the existing range */ + if (PagePrivate(page)) + goto update_bitmap; + + /* Do new allocation to attach subpage */ + ret = btrfs_attach_subpage(fs_info, page); + if (ret < 0) + return ret; + +update_bitmap: + btrfs_subpage_set_tree_block(fs_info, page, eb->start, eb->len); + return 0; } void set_page_extent_mapped(struct page *page) @@ -5063,21 +5083,29 @@ struct extent_buffer *btrfs_clone_extent_buffer(const struct extent_buffer *src) if (new == NULL) return NULL; + set_bit(EXTENT_BUFFER_UPTODATE, &new->bflags); + set_bit(EXTENT_BUFFER_UNMAPPED, &new->bflags); + for (i = 0; i < num_pages; i++) { + int ret; + p = alloc_page(GFP_NOFS); if (!p) { btrfs_release_extent_buffer(new); return NULL; } - attach_extent_buffer_page(new, p); + ret = attach_extent_buffer_page(new, p); + if (ret < 0) { + put_page(p); + btrfs_release_extent_buffer(new); + return NULL; + } WARN_ON(PageDirty(p)); SetPageUptodate(p); new->pages[i] = p; copy_page(page_address(p), page_address(src->pages[i])); } - set_bit(EXTENT_BUFFER_UPTODATE, &new->bflags); - set_bit(EXTENT_BUFFER_UNMAPPED, &new->bflags); return new; } @@ -5316,6 +5344,18 @@ struct extent_buffer *alloc_extent_buffer(struct btrfs_fs_info *fs_info, goto free_eb; } + /* + * Preallocate page->private for subpage case, so that + * we won't allocate memory with private_lock hold. + */ + ret = btrfs_attach_subpage(fs_info, p); + if (ret < 0) { + unlock_page(p); + put_page(p); + exists = ERR_PTR(-ENOMEM); + goto free_eb; + } + spin_lock(&mapping->private_lock); exists = grab_extent_buffer(p); if (exists) { @@ -5325,8 +5365,10 @@ struct extent_buffer *alloc_extent_buffer(struct btrfs_fs_info *fs_info, mark_extent_buffer_accessed(exists, p); goto free_eb; } + /* Should not fail, as we have attached the subpage already */ attach_extent_buffer_page(eb, p); spin_unlock(&mapping->private_lock); + WARN_ON(PageDirty(p)); eb->pages[i] = p; if (!PageUptodate(p)) diff --git a/fs/btrfs/subpage.h b/fs/btrfs/subpage.h index 96f3b226913e..e49d4a7329e1 100644 --- a/fs/btrfs/subpage.h +++ b/fs/btrfs/subpage.h @@ -23,9 +23,59 @@ struct btrfs_subpage { /* Common members for both data and metadata pages */ spinlock_t lock; + union { + /* Structures only used by metadata */ + struct { + u16 tree_block_bitmap; + }; + /* structures only used by data */ + }; }; int btrfs_attach_subpage(struct btrfs_fs_info *fs_info, struct page *page); void btrfs_detach_subpage(struct btrfs_fs_info *fs_info, struct page *page); +/* + * Convert the [start, start + len) range into a u16 bitmap + * + * E.g. if start == page_offset() + 16K, len = 16K, we get 0x00f0. + */ +static inline u16 btrfs_subpage_calc_bitmap(struct btrfs_fs_info *fs_info, + struct page *page, u64 start, u32 len) +{ + int bit_start = offset_in_page(start) >> fs_info->sectorsize_bits; + int nbits = len >> fs_info->sectorsize_bits; + + /* Basic checks */ + ASSERT(PagePrivate(page) && page->private); + ASSERT(IS_ALIGNED(start, fs_info->sectorsize) && + IS_ALIGNED(len, fs_info->sectorsize)); + + /* + * The range check only works for mapped page, we can + * still have unampped page like dummy extent buffer pages. + */ + if (page->mapping) + ASSERT(page_offset(page) <= start && + start + len <= page_offset(page) + PAGE_SIZE); + /* + * Here nbits can be 16, thus can go beyond u16 range. Here we make the + * first left shift to be calculated in unsigned long (u32), then + * truncate the result to u16. + */ + return (u16)(((1UL << nbits) - 1) << bit_start); +} + +static inline void btrfs_subpage_set_tree_block(struct btrfs_fs_info *fs_info, + struct page *page, u64 start, u32 len) +{ + struct btrfs_subpage *subpage = (struct btrfs_subpage *)page->private; + unsigned long flags; + u16 tmp = btrfs_subpage_calc_bitmap(fs_info, page, start, len); + + spin_lock_irqsave(&subpage->lock, flags); + subpage->tree_block_bitmap |= tmp; + spin_unlock_irqrestore(&subpage->lock, flags); +} + #endif /* BTRFS_SUBPAGE_H */ -- 2.29.2
