On Mon, Jun 01, 2015 at 08:52:40PM +0530, Chandan Rajendra wrote: > In the case of subpagesize-blocksize, this patch makes it possible to read > only a single metadata block from the disk instead of all the metadata blocks > that map into a page.
I'm a bit curious about how much benefit is gained from reading a single block rather reading the whole page. Thanks, -liubo > > Signed-off-by: Chandan Rajendra <[email protected]> > --- > fs/btrfs/disk-io.c | 65 +++++++++++++++++++------------ > fs/btrfs/disk-io.h | 3 ++ > fs/btrfs/extent_io.c | 108 > +++++++++++++++++++++++++++++++++++++++++++++++---- > 3 files changed, 144 insertions(+), 32 deletions(-) > > diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c > index 51fe2ec..b794e33 100644 > --- a/fs/btrfs/disk-io.c > +++ b/fs/btrfs/disk-io.c > @@ -597,28 +597,41 @@ static noinline int check_leaf(struct btrfs_root *root, > return 0; > } > > -static int btree_readpage_end_io_hook(struct btrfs_io_bio *io_bio, > - u64 phy_offset, struct page *page, > - u64 start, u64 end, int mirror) > +int verify_extent_buffer_read(struct btrfs_io_bio *io_bio, > + struct page *page, > + u64 start, u64 end, int mirror) > { > - u64 found_start; > - int found_level; > + struct address_space *mapping = > (io_bio->bio).bi_io_vec->bv_page->mapping; > + struct extent_io_tree *tree = &BTRFS_I(mapping->host)->io_tree; > + struct extent_buffer_head *ebh; > struct extent_buffer *eb; > struct btrfs_root *root = BTRFS_I(page->mapping->host)->root; > - int ret = 0; > + unsigned long num_pages; > + unsigned long i; > + u64 found_start; > + int found_level; > int reads_done; > + int ret = 0; > > if (!page->private) > goto out; > > eb = (struct extent_buffer *)page->private; > + do { > + if ((eb->start <= start) && (eb->start + eb->len - 1 > start)) > + break; > + } while ((eb = eb->eb_next) != NULL); > + > + BUG_ON(!eb); > + > + ebh = eb_head(eb); > > /* the pending IO might have been the only thing that kept this buffer > * in memory. Make sure we have a ref for all this other checks > */ > extent_buffer_get(eb); > > - reads_done = atomic_dec_and_test(&eb->io_pages); > + reads_done = atomic_dec_and_test(&ebh->io_bvecs); > if (!reads_done) > goto err; > > @@ -683,28 +696,34 @@ err: > * again, we have to make sure it has something > * to decrement > */ > - atomic_inc(&eb->io_pages); > + atomic_inc(&eb_head(eb)->io_bvecs); > clear_extent_buffer_uptodate(eb); > } > + > + /* > + We never read more than one extent buffer from a page at a time. > + So unlocking the page here should be fine. > + */ > + if (reads_done) { > + num_pages = num_extent_pages(eb->start, eb->len); > + for (i = 0; i < num_pages; i++) { > + page = eb_head(eb)->pages[i]; > + unlock_page(page); > + } > + > + /* > + We don't need to add a check to see if > + extent_io_tree->track_uptodate is set or not, Since > + this function only deals with extent buffers. > + */ > + unlock_extent(tree, eb->start, eb->start + eb->len - 1); > + } > + > free_extent_buffer(eb); > out: > return ret; > } > > -static int btree_io_failed_hook(struct page *page, int failed_mirror) > -{ > - struct extent_buffer *eb; > - struct btrfs_root *root = BTRFS_I(page->mapping->host)->root; > - > - eb = (struct extent_buffer *)page->private; > - set_bit(EXTENT_BUFFER_READ_ERR, &eb->ebflags); > - eb->read_mirror = failed_mirror; > - atomic_dec(&eb->io_pages); > - if (test_and_clear_bit(EXTENT_BUFFER_READAHEAD, &eb->ebflags)) > - btree_readahead_hook(root, eb, eb->start, -EIO); > - return -EIO; /* we fixed nothing */ > -} > - > static void end_workqueue_bio(struct bio *bio, int err) > { > struct btrfs_end_io_wq *end_io_wq = bio->bi_private; > @@ -4349,8 +4368,6 @@ static int btrfs_cleanup_transaction(struct btrfs_root > *root) > } > > static const struct extent_io_ops btree_extent_io_ops = { > - .readpage_end_io_hook = btree_readpage_end_io_hook, > - .readpage_io_failed_hook = btree_io_failed_hook, > .submit_bio_hook = btree_submit_bio_hook, > /* note we're sharing with inode.c for the merge bio hook */ > .merge_bio_hook = btrfs_merge_bio_hook, > diff --git a/fs/btrfs/disk-io.h b/fs/btrfs/disk-io.h > index d4cbfee..c69076c 100644 > --- a/fs/btrfs/disk-io.h > +++ b/fs/btrfs/disk-io.h > @@ -111,6 +111,9 @@ static inline void btrfs_put_fs_root(struct btrfs_root > *root) > kfree(root); > } > > +int verify_extent_buffer_read(struct btrfs_io_bio *io_bio, > + struct page *page, > + u64 start, u64 end, int mirror); > void btrfs_mark_buffer_dirty(struct extent_buffer *buf); > int btrfs_buffer_uptodate(struct extent_buffer *buf, u64 parent_transid, > int atomic); > diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c > index a7e715a..76a6e39 100644 > --- a/fs/btrfs/extent_io.c > +++ b/fs/btrfs/extent_io.c > @@ -14,6 +14,7 @@ > #include "extent_io.h" > #include "extent_map.h" > #include "ctree.h" > +#include "disk-io.h" > #include "btrfs_inode.h" > #include "volumes.h" > #include "check-integrity.h" > @@ -2179,7 +2180,7 @@ int repair_eb_io_failure(struct btrfs_root *root, > struct extent_buffer *eb, > struct page *p = eb_head(eb)->pages[i]; > > ret = repair_io_failure(root->fs_info->btree_inode, start, > - PAGE_CACHE_SIZE, start, p, > + eb->len, start, p, > start - page_offset(p), mirror_num); > if (ret) > break; > @@ -3706,6 +3707,77 @@ lock_extent_buffer_for_io(struct extent_buffer *eb, > return ret; > } > > +static void end_bio_extent_buffer_readpage(struct bio *bio, int err) > +{ > + struct address_space *mapping = bio->bi_io_vec->bv_page->mapping; > + struct extent_io_tree *tree = &BTRFS_I(mapping->host)->io_tree; > + struct btrfs_io_bio *io_bio = btrfs_io_bio(bio); > + struct extent_buffer *eb; > + struct btrfs_root *root; > + struct bio_vec *bvec; > + struct page *page; > + int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags); > + u64 start; > + u64 end; > + int mirror; > + int ret; > + int i; > + > + if (err) > + uptodate = 0; > + > + bio_for_each_segment_all(bvec, bio, i) { > + page = bvec->bv_page; > + root = BTRFS_I(page->mapping->host)->root; > + > + start = page_offset(page) + bvec->bv_offset; > + end = start + bvec->bv_len - 1; > + > + if (!page->private) { > + unlock_page(page); > + unlock_extent(tree, start, end); > + continue; > + } > + > + eb = (struct extent_buffer *)page->private; > + > + do { > + /* > + read_extent_buffer_pages() does not start > + I/O on PG_uptodate pages. Hence the bio may > + map only part of the extent buffer. > + */ > + if ((eb->start <= start) && (eb->start + eb->len - 1 > > start)) > + break; > + } while ((eb = eb->eb_next) != NULL); > + > + BUG_ON(!eb); > + > + mirror = io_bio->mirror_num; > + > + if (uptodate) { > + ret = verify_extent_buffer_read(io_bio, page, start, > + end, mirror); > + if (ret) > + uptodate = 0; > + } > + > + if (!uptodate) { > + set_bit(EXTENT_BUFFER_READ_ERR, &eb->ebflags); > + eb->read_mirror = mirror; > + atomic_dec(&eb_head(eb)->io_bvecs); > + if (test_and_clear_bit(EXTENT_BUFFER_READAHEAD, > + &eb->ebflags)) > + btree_readahead_hook(root, eb, eb->start, > + -EIO); > + ClearPageUptodate(page); > + SetPageError(page); > + } > + } > + > + bio_put(bio); > +} > + > static void end_extent_buffer_writeback(struct extent_buffer *eb) > { > clear_bit(EXTENT_BUFFER_WRITEBACK, &eb->ebflags); > @@ -5330,6 +5402,9 @@ int read_extent_buffer_pages(struct extent_io_tree > *tree, > struct extent_buffer *eb, u64 start, int wait, > get_extent_t *get_extent, int mirror_num) > { > + struct inode *inode = tree->mapping->host; > + struct btrfs_fs_info *fs_info = BTRFS_I(inode)->root->fs_info; > + struct extent_state *cached_state = NULL; > unsigned long i; > unsigned long start_i; > struct page *page; > @@ -5376,15 +5451,31 @@ int read_extent_buffer_pages(struct extent_io_tree > *tree, > > clear_bit(EXTENT_BUFFER_READ_ERR, &eb->ebflags); > eb->read_mirror = 0; > - atomic_set(&eb->io_pages, num_reads); > + atomic_set(&eb_head(eb)->io_bvecs, num_reads); > for (i = start_i; i < num_pages; i++) { > page = eb_head(eb)->pages[i]; > if (!PageUptodate(page)) { > ClearPageError(page); > - err = __extent_read_full_page(tree, page, > - get_extent, &bio, > - mirror_num, &bio_flags, > - READ | REQ_META); > + if (eb->len < PAGE_CACHE_SIZE) { > + lock_extent_bits(tree, eb->start, eb->start + > eb->len - 1, 0, > + &cached_state); > + err = submit_extent_page(READ | REQ_META, tree, > + page, eb->start >> 9, > + eb->len, eb->start - > page_offset(page), > + > fs_info->fs_devices->latest_bdev, > + &bio, -1, > end_bio_extent_buffer_readpage, > + mirror_num, bio_flags, > bio_flags); > + } else { > + lock_extent_bits(tree, page_offset(page), > + page_offset(page) + > PAGE_CACHE_SIZE - 1, > + 0, &cached_state); > + err = submit_extent_page(READ | REQ_META, tree, > + page, page_offset(page) > >> 9, > + PAGE_CACHE_SIZE, 0, > + > fs_info->fs_devices->latest_bdev, > + &bio, -1, > end_bio_extent_buffer_readpage, > + mirror_num, bio_flags, > bio_flags); > + } > if (err) > ret = err; > } else { > @@ -5405,10 +5496,11 @@ int read_extent_buffer_pages(struct extent_io_tree > *tree, > for (i = start_i; i < num_pages; i++) { > page = eb_head(eb)->pages[i]; > wait_on_page_locked(page); > - if (!PageUptodate(page)) > - ret = -EIO; > } > > + if (!extent_buffer_uptodate(eb)) > + ret = -EIO; > + > return ret; > > unlock_exit: > -- > 2.1.0 > -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
