diff options
| -rw-r--r-- | fs/btrfs/extent_io.c | 30 | ||||
| -rw-r--r-- | fs/btrfs/subpage.c | 19 | ||||
| -rw-r--r-- | fs/btrfs/subpage.h | 9 |
3 files changed, 32 insertions, 26 deletions
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c index 1acbb7f1e6e3..9e81d25dea70 100644 --- a/fs/btrfs/extent_io.c +++ b/fs/btrfs/extent_io.c @@ -2687,21 +2687,6 @@ static void end_page_read(struct page *page, bool uptodate, u64 start, u32 len) ASSERT(page_offset(page) <= start && start + len <= page_offset(page) + PAGE_SIZE); - /* - * For subapge metadata case, all btrfs_page_* helpers need page to - * have page::private populated. - * But we can have rare case where the last eb in the page is only - * referred by the IO, and it gets released immedately after it's - * read and verified. - * - * This can detach the page private completely. - * In that case, we can just skip the page status update completely, - * as the page has no eb anymore. - */ - if (fs_info->sectorsize < PAGE_SIZE && unlikely(!PagePrivate(page))) { - ASSERT(!is_data_inode(page->mapping->host)); - return; - } if (uptodate) { btrfs_page_set_uptodate(fs_info, page, start, len); } else { @@ -2711,11 +2696,7 @@ static void end_page_read(struct page *page, bool uptodate, u64 start, u32 len) if (fs_info->sectorsize == PAGE_SIZE) unlock_page(page); - else if (is_data_inode(page->mapping->host)) - /* - * For subpage data, unlock the page if we're the last reader. - * For subpage metadata, page lock is not utilized for read. - */ + else btrfs_subpage_end_reader(fs_info, page, start, len); } @@ -5603,6 +5584,12 @@ static bool page_range_has_eb(struct btrfs_fs_info *fs_info, struct page *page) subpage = (struct btrfs_subpage *)page->private; if (atomic_read(&subpage->eb_refs)) return true; + /* + * Even there is no eb refs here, we may still have + * end_page_read() call relying on page::private. + */ + if (atomic_read(&subpage->readers)) + return true; } return false; } @@ -5663,7 +5650,7 @@ static void detach_extent_buffer_page(struct extent_buffer *eb, struct page *pag /* * We can only detach the page private if there are no other ebs in the - * page range. + * page range and no unfinished IO. */ if (!page_range_has_eb(fs_info, page)) btrfs_detach_subpage(fs_info, page); @@ -6381,6 +6368,7 @@ static int read_extent_buffer_subpage(struct extent_buffer *eb, int wait, check_buffer_tree_ref(eb); btrfs_subpage_clear_error(fs_info, page, eb->start, eb->len); + btrfs_subpage_start_reader(fs_info, page, eb->start, eb->len); ret = submit_extent_page(REQ_OP_READ | REQ_META, NULL, &bio_ctrl, page, eb->start, eb->len, eb->start - page_offset(page), diff --git a/fs/btrfs/subpage.c b/fs/btrfs/subpage.c index 7d72eaf5f972..640bcd21bf28 100644 --- a/fs/btrfs/subpage.c +++ b/fs/btrfs/subpage.c @@ -3,6 +3,7 @@ #include <linux/slab.h> #include "ctree.h" #include "subpage.h" +#include "btrfs_inode.h" /* * Subpage (sectorsize < PAGE_SIZE) support overview: @@ -185,12 +186,10 @@ void btrfs_subpage_start_reader(const struct btrfs_fs_info *fs_info, { struct btrfs_subpage *subpage = (struct btrfs_subpage *)page->private; const int nbits = len >> fs_info->sectorsize_bits; - int ret; btrfs_subpage_assert(fs_info, page, start, len); - ret = atomic_add_return(nbits, &subpage->readers); - ASSERT(ret == nbits); + atomic_add(nbits, &subpage->readers); } void btrfs_subpage_end_reader(const struct btrfs_fs_info *fs_info, @@ -198,10 +197,22 @@ void btrfs_subpage_end_reader(const struct btrfs_fs_info *fs_info, { struct btrfs_subpage *subpage = (struct btrfs_subpage *)page->private; const int nbits = len >> fs_info->sectorsize_bits; + bool is_data; + bool last; btrfs_subpage_assert(fs_info, page, start, len); + is_data = is_data_inode(page->mapping->host); ASSERT(atomic_read(&subpage->readers) >= nbits); - if (atomic_sub_and_test(nbits, &subpage->readers)) + last = atomic_sub_and_test(nbits, &subpage->readers); + + /* + * For data we need to unlock the page if the last read has finished. + * + * And please don't replace @last with atomic_sub_and_test() call + * inside if () condition. + * As we want the atomic_sub_and_test() to be always executed. + */ + if (is_data && last) unlock_page(page); } diff --git a/fs/btrfs/subpage.h b/fs/btrfs/subpage.h index 65298a5efe7b..4d7aca85d915 100644 --- a/fs/btrfs/subpage.h +++ b/fs/btrfs/subpage.h @@ -22,6 +22,14 @@ struct btrfs_subpage { u16 error_bitmap; u16 dirty_bitmap; u16 writeback_bitmap; + /* + * Both data and metadata needs to track how many readers are for the + * page. + * Data relies on @readers to unlock the page when last reader finished. + * While metadata doesn't need page unlock, it needs to prevent + * page::private get cleared before the last end_page_read(). + */ + atomic_t readers; union { /* * Structures only used by metadata @@ -32,7 +40,6 @@ struct btrfs_subpage { atomic_t eb_refs; /* Structures only used by data */ struct { - atomic_t readers; atomic_t writers; /* Tracke pending ordered extent in this sector */ |