On Tuesday, July 26, 2016 12:11:49 PM Josef Bacik wrote:
> On 07/04/2016 12:34 AM, Chandan Rajendra wrote:
> > For the subpage-blocksize scenario, a page can contain multiple
> > blocks. In such cases, this patch handles reading data from files.
> >
> > To track the status of individual blocks of a page, this patch makes use
> > of a bitmap pointed to by the newly introduced per-page 'struct
> > btrfs_page_private'.
> >
> > The per-page btrfs_page_private->io_lock plays the same role as
> > BH_Uptodate_Lock (see end_buffer_async_read()) i.e. without the io_lock
> > we may end up in the following situation,
> >
> > NOTE: Assume 64k page size and 4k block size. Also assume that the first
> > 12 blocks of the page are contiguous while the next 4 blocks are
> > contiguous. When reading the page we end up submitting two "logical
> > address space" bios. So end_bio_extent_readpage function is invoked
> > twice, once for each bio.
> >
> > |-------------------------+-------------------------+-------------|
> > | Task A | Task B | Task C |
> > |-------------------------+-------------------------+-------------|
> > | end_bio_extent_readpage | | |
> > | process block 0 | | |
> > | - clear BLK_STATE_IO | | |
> > | - page_read_complete | | |
> > | process block 1 | | |
> > | | | |
> > | | | |
> > | | end_bio_extent_readpage | |
> > | | process block 0 | |
> > | | - clear BLK_STATE_IO | |
> > | | - page_read_complete | |
> > | | process block 1 | |
> > | | | |
> > | process block 11 | process block 3 | |
> > | - clear BLK_STATE_IO | - clear BLK_STATE_IO | |
> > | - page_read_complete | - page_read_complete | |
> > | - returns true | - returns true | |
> > | - unlock_page() | | |
> > | | | lock_page() |
> > | | - unlock_page() | |
> > |-------------------------+-------------------------+-------------|
> >
> > We end up incorrectly unlocking the page twice and "Task C" ends up
> > working on an unlocked page. So private->io_lock makes sure that only
> > one of the tasks gets "true" as the return value when page_io_complete()
> > is invoked. As an optimization the patch gets the io_lock only when the
> > last block of the bio_vec is being processed.
> >
> > Signed-off-by: Chandan Rajendra <[email protected]>
> > ---
> > fs/btrfs/extent_io.c | 371
> > ++++++++++++++++++++++++++++++++++++---------------
> > fs/btrfs/extent_io.h | 74 +++++++++-
> > fs/btrfs/inode.c | 16 +--
> > 3 files changed, 338 insertions(+), 123 deletions(-)
> >
> > diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
> > index e197d47..a349f99 100644
> > --- a/fs/btrfs/extent_io.c
> > +++ b/fs/btrfs/extent_io.c
> > @@ -24,6 +24,7 @@
> >
> > static struct kmem_cache *extent_state_cache;
> > static struct kmem_cache *extent_buffer_cache;
> > +static struct kmem_cache *page_private_cache;
> > static struct bio_set *btrfs_bioset;
> >
> > static inline bool extent_state_in_tree(const struct extent_state *state)
> > @@ -174,10 +175,16 @@ int __init extent_io_init(void)
> > if (!extent_buffer_cache)
> > goto free_state_cache;
> >
> > + page_private_cache = kmem_cache_create("btrfs_page_private",
> > + sizeof(struct btrfs_page_private), 0,
> > + SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD, NULL);
> > + if (!page_private_cache)
> > + goto free_buffer_cache;
> > +
> > btrfs_bioset = bioset_create(BIO_POOL_SIZE,
> > offsetof(struct btrfs_io_bio, bio));
> > if (!btrfs_bioset)
> > - goto free_buffer_cache;
> > + goto free_page_private_cache;
> >
> > if (bioset_integrity_create(btrfs_bioset, BIO_POOL_SIZE))
> > goto free_bioset;
> > @@ -188,6 +195,10 @@ free_bioset:
> > bioset_free(btrfs_bioset);
> > btrfs_bioset = NULL;
> >
> > +free_page_private_cache:
> > + kmem_cache_destroy(page_private_cache);
> > + page_private_cache = NULL;
> > +
> > free_buffer_cache:
> > kmem_cache_destroy(extent_buffer_cache);
> > extent_buffer_cache = NULL;
> > @@ -1323,6 +1334,95 @@ int clear_record_extent_bits(struct extent_io_tree
> > *tree, u64 start, u64 end,
> > changeset);
> > }
> >
> > +static int modify_page_blks_state(struct page *page,
> > + unsigned long blk_states,
> > + u64 start, u64 end, int set)
> > +{
> > + struct inode *inode = page->mapping->host;
> > + unsigned long *bitmap;
> > + unsigned long first_state;
> > + unsigned long state;
> > + u64 nr_blks;
> > + u64 blk;
> > +
> > + ASSERT(BTRFS_I(inode)->root->sectorsize < PAGE_SIZE);
> > +
> > + bitmap = ((struct btrfs_page_private *)page->private)->bstate;
> > +
> > + blk = BTRFS_BYTES_TO_BLKS(BTRFS_I(inode)->root->fs_info,
> > + start & (PAGE_SIZE - 1));
> > + nr_blks = BTRFS_BYTES_TO_BLKS(BTRFS_I(inode)->root->fs_info,
> > + (end - start + 1));
> > +
> > + first_state = find_next_bit(&blk_states, BLK_NR_STATE, 0);
> > +
> > + while (nr_blks--) {
> > + state = first_state;
> > +
> > + while (state < BLK_NR_STATE) {
> > + if (set)
> > + set_bit((blk * BLK_NR_STATE) + state, bitmap);
> > + else
> > + clear_bit((blk * BLK_NR_STATE) + state, bitmap);
> > +
> > + state = find_next_bit(&blk_states, BLK_NR_STATE,
> > + state + 1);
> > + }
> > +
> > + ++blk;
> > + }
> > +
> > + return 0;
> > +}
> > +
> > +int set_page_blks_state(struct page *page, unsigned long blk_states,
> > + u64 start, u64 end)
> > +{
> > + return modify_page_blks_state(page, blk_states, start, end, 1);
> > +}
> > +
> > +int clear_page_blks_state(struct page *page, unsigned long blk_states,
> > + u64 start, u64 end)
> > +{
> > + return modify_page_blks_state(page, blk_states, start, end, 0);
> > +}
> > +
> > +int test_page_blks_state(struct page *page, enum blk_state blk_state,
> > + u64 start, u64 end, int check_all)
> > +{
> > + struct inode *inode = page->mapping->host;
> > + unsigned long *bitmap;
> > + unsigned long blk;
> > + u64 nr_blks;
> > + int found = 0;
> > +
> > + ASSERT(BTRFS_I(inode)->root->sectorsize < PAGE_SIZE);
> > +
> > + bitmap = ((struct btrfs_page_private *)page->private)->bstate;
> > +
> > + blk = BTRFS_BYTES_TO_BLKS(BTRFS_I(inode)->root->fs_info,
> > + start & (PAGE_SIZE - 1));
> > + nr_blks = BTRFS_BYTES_TO_BLKS(BTRFS_I(inode)->root->fs_info,
> > + (end - start + 1));
> > +
> > + while (nr_blks--) {
> > + if (test_bit((blk * BLK_NR_STATE) + blk_state, bitmap)) {
> > + if (!check_all)
> > + return 1;
> > + found = 1;
> > + } else if (check_all) {
> > + return 0;
> > + }
> > +
> > + ++blk;
> > + }
> > +
> > + if (!check_all && !found)
> > + return 0;
> > +
> > + return 1;
> > +}
> > +
> > /*
> > * either insert or lock state struct between start and end use mask to
> > tell
> > * us if waiting is desired.
> > @@ -1966,14 +2066,27 @@ int test_range_bit(struct extent_io_tree *tree, u64
> > start, u64 end,
> > * helper function to set a given page up to date if all the
> > * extents in the tree for that page are up to date
> > */
> > -static void check_page_uptodate(struct extent_io_tree *tree, struct page
> > *page)
> > +static void check_page_uptodate(struct page *page)
> > {
> > + struct inode *inode = page->mapping->host;
> > + struct btrfs_root *root = BTRFS_I(inode)->root;
> > u64 start = page_offset(page);
> > u64 end = start + PAGE_SIZE - 1;
> > - if (test_range_bit(tree, start, end, EXTENT_UPTODATE, 1, NULL))
> > +
> > + if (root->sectorsize == PAGE_SIZE
> > + || test_page_blks_state(page, BLK_STATE_UPTODATE, start,
> > + end, 1))
> > SetPageUptodate(page);
> > }
>
> This drops the test_range_bit() for the normal case, did you mean to do that?
>
> Actually reading down it looks like you are dropping the EXTENT_UPTODATE bit
> altogether for the sectorsize == PAGE_SIZE case. I like this idea, but I'm a
> little wary of it. Could we perhaps get that broken out into a different
> patch
> so if we need to bisect a weird problem and that was it we can find that it
> was
> actually that change?
Josef, you are right. For sectorsize == PAGE_SIZE scenario, this patch now
uses PG_Uptodate page flag to track file block uptodate status.
I will split the corresponding code into a new patch.
>
> >
> > +static int page_io_complete(struct page *page)
> > +{
> > + u64 start = page_offset(page);
> > + u64 end = start + PAGE_SIZE - 1;
> > +
> > + return !test_page_blks_state(page, BLK_STATE_IO, start, end, 0);
> > +}
> > +
> > int free_io_failure(struct inode *inode, struct io_failure_record *rec)
> > {
> > int ret;
> > @@ -2299,7 +2412,9 @@ int btrfs_check_repairable(struct inode *inode,
> > struct bio *failed_bio,
> > * a) deliver good data to the caller
> > * b) correct the bad sectors on disk
> > */
> > - if (failed_bio->bi_vcnt > 1) {
> > + if ((failed_bio->bi_vcnt > 1)
> > + || (failed_bio->bi_io_vec->bv_len
> > + > BTRFS_I(inode)->root->sectorsize)) {
> > /*
> > * to fulfill b), we need to know the exact failing sectors, as
> > * we don't want to rewrite any more than the failed ones. thus,
> > @@ -2505,18 +2620,6 @@ static void end_bio_extent_writepage(struct bio *bio)
> > bio_put(bio);
> > }
> >
> > -static void
> > -endio_readpage_release_extent(struct extent_io_tree *tree, u64 start, u64
> > len,
> > - int uptodate)
> > -{
> > - struct extent_state *cached = NULL;
> > - u64 end = start + len - 1;
> > -
> > - if (uptodate && tree->track_uptodate)
> > - set_extent_uptodate(tree, start, end, &cached, GFP_ATOMIC);
> > - unlock_extent_cached(tree, start, end, &cached, GFP_ATOMIC);
> > -}
> > -
>
> This is what worries me especially, I'm unsure if we need to track uptodate
> for
> the io_failure_tree or not. Really if we don' then rip it all out, but make
> it
> separate.
We don't need to track uptodate status for io_failure_tree. I will create a
new patch to get that done.
>
> > /*
> > * after a readpage IO is done, we need to:
> > * clear the uptodate bits on error
> > @@ -2533,67 +2636,50 @@ static void end_bio_extent_readpage(struct bio *bio)
> > struct bio_vec *bvec;
> > int uptodate = !bio->bi_error;
> > struct btrfs_io_bio *io_bio = btrfs_io_bio(bio);
> > + struct extent_state *cached = NULL;
> > + struct btrfs_page_private *pg_private;
> > struct extent_io_tree *tree;
> > + unsigned long flags;
> > u64 offset = 0;
> > u64 start;
> > u64 end;
> > - u64 len;
> > - u64 extent_start = 0;
> > - u64 extent_len = 0;
> > + int nr_sectors;
> > int mirror;
> > + int unlock;
> > int ret;
> > int i;
> >
> > bio_for_each_segment_all(bvec, bio, i) {
> > struct page *page = bvec->bv_page;
> > struct inode *inode = page->mapping->host;
> > + struct btrfs_root *root = BTRFS_I(inode)->root;
> >
> > pr_debug("end_bio_extent_readpage: bi_sector=%llu, err=%d, "
> > "mirror=%u\n", (u64)bio->bi_iter.bi_sector,
> > bio->bi_error, io_bio->mirror_num);
> > tree = &BTRFS_I(inode)->io_tree;
> >
> > - /* We always issue full-page reads, but if some block
> > - * in a page fails to read, blk_update_request() will
> > - * advance bv_offset and adjust bv_len to compensate.
> > - * Print a warning for nonzero offsets, and an error
> > - * if they don't add up to a full page. */
> > - if (bvec->bv_offset || bvec->bv_len != PAGE_SIZE) {
> > - if (bvec->bv_offset + bvec->bv_len != PAGE_SIZE)
> > -
> > btrfs_err(BTRFS_I(page->mapping->host)->root->fs_info,
> > - "partial page read in btrfs with offset %u
> > and length %u",
> > - bvec->bv_offset, bvec->bv_len);
> > - else
> > -
> > btrfs_info(BTRFS_I(page->mapping->host)->root->fs_info,
> > - "incomplete page read in btrfs with offset
> > %u and "
> > - "length %u",
> > - bvec->bv_offset, bvec->bv_len);
> > - }
> > -
> > - start = page_offset(page);
> > - end = start + bvec->bv_offset + bvec->bv_len - 1;
> > - len = bvec->bv_len;
> > -
> > + start = page_offset(page) + bvec->bv_offset;
> > + end = start + bvec->bv_len - 1;
>
> Ok so you set end to the end of the bvec, but you don't actually use end
> anywhere else down below, since we are now doing things per sector. So
> perhaps
> instead use it to indicate the end of the sector, so you don't have a bunch of
>
> start + root->sectorsize - 1
>
> statements everywhere.
I agree. I will fix this.
>
> > + nr_sectors = BTRFS_BYTES_TO_BLKS(root->fs_info,
> > + bvec->bv_len);
> > mirror = io_bio->mirror_num;
> > +
> > +next_block:
> > if (likely(uptodate && tree->ops &&
> > tree->ops->readpage_end_io_hook)) {
> > ret = tree->ops->readpage_end_io_hook(io_bio, offset,
> > - page, start, end,
> > - mirror);
> > + page, start,
> > + start +
> > root->sectorsize - 1,
> > + mirror);
> > if (ret)
> > uptodate = 0;
> > else
> > - clean_io_failure(inode, start, page, 0);
> > + clean_io_failure(inode, start, page,
> > + start - page_offset(page));
> > }
> >
> > - if (likely(uptodate))
> > - goto readpage_ok;
> > -
> > - if (tree->ops && tree->ops->readpage_io_failed_hook) {
> > - ret = tree->ops->readpage_io_failed_hook(page, mirror);
> > - if (!ret && !bio->bi_error)
> > - uptodate = 1;
> > - } else {
> > + if (!uptodate) {
> > /*
> > * The generic bio_readpage_error handles errors the
> > * following way: If possible, new read requests are
> > @@ -2604,58 +2690,69 @@ static void end_bio_extent_readpage(struct bio *bio)
> > * can't handle the error it will return -EIO and we
> > * remain responsible for that page.
> > */
> > - ret = bio_readpage_error(bio, offset, page, start, end,
> > - mirror);
> > + ret = bio_readpage_error(bio, offset, page,
> > + start, start + root->sectorsize
> > - 1,
> > + mirror);
> > if (ret == 0) {
> > uptodate = !bio->bi_error;
> > - offset += len;
> > - continue;
> > + offset += root->sectorsize;
> > + if (--nr_sectors) {
> > + start += root->sectorsize;
> > + goto next_block;
> > + } else {
> > + continue;
> > + }
> > }
> > }
> > -readpage_ok:
> > - if (likely(uptodate)) {
> > - loff_t i_size = i_size_read(inode);
> > - pgoff_t end_index = i_size >> PAGE_SHIFT;
> > - unsigned off;
> > -
> > - /* Zero out the end if this page straddles i_size */
> > - off = i_size & (PAGE_SIZE-1);
> > - if (page->index == end_index && off)
> > - zero_user_segment(page, off, PAGE_SIZE);
> > - SetPageUptodate(page);
> > +
> > + if (uptodate) {
> > + if (root->sectorsize < PAGE_SIZE)
> > + set_page_blks_state(page,
> > + 1 << BLK_STATE_UPTODATE, start,
> > + start + root->sectorsize - 1);
> > + check_page_uptodate(page);
> > } else {
> > ClearPageUptodate(page);
> > SetPageError(page);
> > }
> > - unlock_page(page);
> > - offset += len;
> > -
> > - if (unlikely(!uptodate)) {
> > - if (extent_len) {
> > - endio_readpage_release_extent(tree,
> > - extent_start,
> > - extent_len, 1);
> > - extent_start = 0;
> > - extent_len = 0;
> > - }
> > - endio_readpage_release_extent(tree, start,
> > - end - start + 1, 0);
> > - } else if (!extent_len) {
> > - extent_start = start;
> > - extent_len = end + 1 - start;
> > - } else if (extent_start + extent_len == start) {
> > - extent_len += end + 1 - start;
> > - } else {
> > - endio_readpage_release_extent(tree, extent_start,
> > - extent_len, uptodate);
> > - extent_start = start;
> > - extent_len = end + 1 - start;
> > +
> > + offset += root->sectorsize;
> > +
> > + if (--nr_sectors) {
> > + if (root->sectorsize < PAGE_SIZE)
> > + clear_page_blks_state(page, 1 << BLK_STATE_IO,
> > + start,
> > + start + root->sectorsize - 1);
> > + clear_extent_bit(tree, start, start + root->sectorsize
> > - 1,
> > + EXTENT_LOCKED, 1, 0, &cached,
> > GFP_ATOMIC);
> > + start += root->sectorsize;
> > + goto next_block;
> > }
> > +
> > + WARN_ON(!PagePrivate(page));
> > +
> > + unlock = 1;
> > +
> > + if (root->sectorsize < PAGE_SIZE) {
> > + pg_private = (struct btrfs_page_private *)page->private;
> > +
> > + spin_lock_irqsave(&pg_private->io_lock, flags);
> > +
> > + clear_page_blks_state(page, 1 << BLK_STATE_IO,
> > + start, start + root->sectorsize - 1);
> > +
> > + unlock = page_io_complete(page);
> > +
> > + spin_unlock_irqrestore(&pg_private->io_lock, flags);
> > + }
> > +
> > + clear_extent_bit(tree, start, start + root->sectorsize - 1,
> > + EXTENT_LOCKED, 1, 0, &cached, GFP_ATOMIC);
> > +
> > + if (unlock)
> > + unlock_page(page);
> > }
> >
> > - if (extent_len)
> > - endio_readpage_release_extent(tree, extent_start, extent_len,
> > - uptodate);
> > if (io_bio->end_io)
> > io_bio->end_io(io_bio, bio->bi_error);
> > bio_put(bio);
> > @@ -2844,13 +2941,51 @@ static void attach_extent_buffer_page(struct
> > extent_buffer *eb,
> > }
> > }
> >
> > -void set_page_extent_mapped(struct page *page)
> > +int set_page_extent_mapped(struct page *page)
> > {
> > + struct inode *inode = page->mapping->host;
> > + struct btrfs_root *root = BTRFS_I(inode)->root;
> > + struct btrfs_page_private *pg_private;
> > + unsigned long private = EXTENT_PAGE_PRIVATE;
> > +
> > if (!PagePrivate(page)) {
> > + if (root->sectorsize < PAGE_SIZE) {
> > + pg_private = kmem_cache_zalloc(page_private_cache,
> > + GFP_NOFS);
> > + if (!pg_private)
> > + return -ENOMEM;
> > +
> > + spin_lock_init(&pg_private->io_lock);
> > +
> > + private = (unsigned long)pg_private;
> > + }
> > +
> > SetPagePrivate(page);
> > get_page(page);
> > - set_page_private(page, EXTENT_PAGE_PRIVATE);
> > + set_page_private(page, private);
> > + }
> > +
> > + return 0;
> > +}
> > +
> > +int clear_page_extent_mapped(struct page *page)
> > +{
> > + struct inode *inode = page->mapping->host;
> > + struct btrfs_root *root = BTRFS_I(inode)->root;
> > + struct btrfs_page_private *pg_private;
> > +
> > + if (PagePrivate(page)) {
> > + if (root->sectorsize < PAGE_SIZE) {
> > + pg_private = (struct btrfs_page_private
> > *)(page->private);
> > + kmem_cache_free(page_private_cache, pg_private);
> > + }
> > +
> > + ClearPagePrivate(page);
> > + set_page_private(page, 0);
> > + put_page(page);
> > }
> > +
> > + return 0;
> > }
> >
> > static struct extent_map *
> > @@ -2896,6 +3031,7 @@ static int __do_readpage(struct extent_io_tree *tree,
> > u64 *prev_em_start)
> > {
> > struct inode *inode = page->mapping->host;
> > + struct btrfs_root *root = BTRFS_I(inode)->root;
> > u64 start = page_offset(page);
> > u64 page_end = start + PAGE_SIZE - 1;
> > u64 end;
> > @@ -2918,13 +3054,6 @@ static int __do_readpage(struct extent_io_tree *tree,
> > set_page_extent_mapped(page);
> >
> > end = page_end;
> > - if (!PageUptodate(page)) {
> > - if (cleancache_get_page(page) == 0) {
> > - BUG_ON(blocksize != PAGE_SIZE);
> > - unlock_extent(tree, start, end);
> > - goto out;
> > - }
> > - }
>
> Why are we deleting this here? I don't understand why we can't still use
> cleancache_get_page(). I'm sure there's a reason, I'd just like to know what
> it is.
>
> >
> > if (page->index == last_byte >> PAGE_SHIFT) {
> > char *userpage;
> > @@ -2944,18 +3073,18 @@ static int __do_readpage(struct extent_io_tree
> > *tree,
> >
> > if (cur >= last_byte) {
> > char *userpage;
> > - struct extent_state *cached = NULL;
> >
> > iosize = PAGE_SIZE - pg_offset;
> > userpage = kmap_atomic(page);
> > memset(userpage + pg_offset, 0, iosize);
> > flush_dcache_page(page);
> > kunmap_atomic(userpage);
> > - set_extent_uptodate(tree, cur, cur + iosize - 1,
> > - &cached, GFP_NOFS);
> > + if (root->sectorsize < PAGE_SIZE)
> > + set_page_blks_state(page, 1 <<
> > BLK_STATE_UPTODATE, cur,
> > + cur + iosize - 1);
>
> Can we maybe push the if (root->sectorisze < PAGE_SIZE) check into the
> page_blks_state helpers instead so we can just call the function and assume
> things will work out right?
I did try to implement it. But in the next patch i.e. "Btrfs:
subpage-blocksize: Fix whole page write" we have code such as the
following ...
if (root->sectorsize < PAGE_SIZE) {
clear_page_blks_state(page, 1 << BLK_STATE_IO, start,
end);
clear_writeback = page_io_complete(page);
spin_unlock_irqrestore(&pg_private->io_lock, flags);
}
In such cases, we still need the explicit "root->sectorsize < PAGE_SIZE"
checks outside [set|clear]_page_blks_state() functions.
>
> > unlock_extent_cached(tree, cur,
> > cur + iosize - 1,
> > - &cached, GFP_NOFS);
> > + NULL, GFP_NOFS);
> > break;
> > }
> > em = __get_extent_map(inode, page, pg_offset, cur,
> > @@ -2990,6 +3119,13 @@ static int __do_readpage(struct extent_io_tree *tree,
> > if (test_bit(EXTENT_FLAG_PREALLOC, &em->flags))
> > block_start = EXTENT_MAP_HOLE;
> >
> > + if ((block_start != EXTENT_MAP_HOLE) &&
> > + (blocksize == PAGE_SIZE) && !PageUptodate(page) &&
> > + (cleancache_get_page(page) == 0)) {
> > + unlock_extent(tree, cur, end);
> > + break;
> > + }
> > +
>
> Huh? Maybe just a comment here.
>
The above logic was derived from the following code snippet in
do_mpage_readpage() ...
if (fully_mapped && blocks_per_page == 1 && !PageUptodate(page) &&
cleancache_get_page(page) == 0) {
SetPageUptodate(page);
goto confused;
}
I admit that I don't understand as to why a file block has to be 'fully
mapped' (i.e. a file block should not be a hole) for using a page from
cleancache. That was the only reason to move the invocation of
cleancache_get_page() to the new location.
However the other check is required since cleancache operates on page sized
granularity.
> > /*
> > * If we have a file range that points to a compressed extent
> > * and it's followed by a consecutive file range that points to
> > @@ -3045,8 +3181,11 @@ static int __do_readpage(struct extent_io_tree *tree,
> > flush_dcache_page(page);
> > kunmap_atomic(userpage);
> >
> > - set_extent_uptodate(tree, cur, cur + iosize - 1,
> > - &cached, GFP_NOFS);
> > + if (root->sectorsize < PAGE_SIZE)
> > + set_page_blks_state(page,
> > + 1 << BLK_STATE_UPTODATE, cur,
> > + cur + iosize - 1);
> > +
> > unlock_extent_cached(tree, cur,
> > cur + iosize - 1,
> > &cached, GFP_NOFS);
> > @@ -3055,9 +3194,13 @@ static int __do_readpage(struct extent_io_tree *tree,
> > continue;
> > }
> > /* the get_extent function already copied into the page */
> > - if (test_range_bit(tree, cur, cur_end,
> > - EXTENT_UPTODATE, 1, NULL)) {
> > - check_page_uptodate(tree, page);
> > + if ((root->sectorsize == PAGE_SIZE
> > + && PageUptodate(page))
> > + || (root->sectorsize < PAGE_SIZE
> > + && test_page_blks_state(page,
> > + BLK_STATE_UPTODATE, cur,
> > + cur_end, 1))) {
> > + check_page_uptodate(page);
> > unlock_extent(tree, cur, cur + iosize - 1);
> > cur = cur + iosize;
> > pg_offset += iosize;
> > @@ -3075,6 +3218,9 @@ static int __do_readpage(struct extent_io_tree *tree,
> > }
> >
> > pnr -= page->index;
> > + if (root->sectorsize < PAGE_SIZE)
> > + set_page_blks_state(page, 1 << BLK_STATE_IO, cur,
> > + cur + iosize - 1);
> > ret = submit_extent_page(rw, tree, NULL, page,
> > sector, disk_io_size, pg_offset,
> > bdev, bio, pnr,
> > @@ -3087,12 +3233,15 @@ static int __do_readpage(struct extent_io_tree
> > *tree,
> > *bio_flags = this_bio_flag;
> > } else {
> > SetPageError(page);
> > + if (root->sectorsize < PAGE_SIZE)
> > + clear_page_blks_state(page, 1 << BLK_STATE_IO,
> > + cur, cur + iosize - 1);
> > unlock_extent(tree, cur, cur + iosize - 1);
> > }
> > cur = cur + iosize;
> > pg_offset += iosize;
> > }
> > -out:
> > +
> > if (!nr) {
> > if (!PageError(page))
> > SetPageUptodate(page);
> > diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
> > index db30270..c08a8ab 100644
> > --- a/fs/btrfs/extent_io.h
> > +++ b/fs/btrfs/extent_io.h
> > @@ -53,11 +53,71 @@
> > #define PAGE_SET_ERROR (1 << 5)
> >
> > /*
> > - * page->private values. Every page that is controlled by the extent
> > - * map has page->private set to one.
> > + * page->private values for "sector size" == "page size" case. Every
> > + * page that is controlled by the extent map has page->private set to
> > + * one.
> > */
> > #define EXTENT_PAGE_PRIVATE 1
> >
> > +enum blk_state {
> > + BLK_STATE_UPTODATE,
> > + BLK_STATE_DIRTY,
> > + BLK_STATE_IO,
> > + BLK_NR_STATE,
> > +};
> > +
> > +/*
> > + The maximum number of blocks per page (i.e. 32) occurs when using 2k
> > + as the block size and having 64k as the page size.
> > +*/
> > +#define BLK_STATE_NR_LONGS DIV_ROUND_UP(BLK_NR_STATE * 32, BITS_PER_LONG)
> > +
> > +/*
> > + btrfs_page_private->io_lock plays the same role as BH_Uptodate_Lock
> > + (see end_buffer_async_read()) i.e. without the io_lock we may end up
> > + in the following situation,
> > +
> > + NOTE: Assume 64k page size and 4k block size. Also assume that the first
> > 12
> > + blocks of the page are contiguous while the next 4 blocks are
> > contiguous. When
> > + reading the page we end up submitting two "logical address space" bios.
> > So
> > + end_bio_extent_readpage function is invoked twice, once for each bio.
> > +
> > + |-------------------------+-------------------------+-------------|
> > + | Task A | Task B | Task C |
> > + |-------------------------+-------------------------+-------------|
> > + | end_bio_extent_readpage | | |
> > + | process block 0 | | |
> > + | - clear BLK_STATE_IO | | |
> > + | - page_read_complete | | |
> > + | process block 1 | | |
> > + | | | |
> > + | | | |
> > + | | end_bio_extent_readpage | |
> > + | | process block 0 | |
> > + | | - clear BLK_STATE_IO | |
> > + | | - page_read_complete | |
> > + | | process block 1 | |
> > + | | | |
> > + | process block 11 | process block 3 | |
> > + | - clear BLK_STATE_IO | - clear BLK_STATE_IO | |
> > + | - page_read_complete | - page_read_complete | |
> > + | - returns true | - returns true | |
> > + | - unlock_page() | | |
> > + | | | lock_page() |
> > + | | - unlock_page() | |
> > + |-------------------------+-------------------------+-------------|
> > +
> > + We end up incorrectly unlocking the page twice and "Task C" ends up
> > + working on an unlocked page. So private->io_lock makes sure that
> > + only one of the tasks gets "true" as the return value when
> > + page_io_complete() is invoked. As an optimization the patch gets the
> > + io_lock only when the last block of the bio_vec is being processed.
> > +*/
> > +struct btrfs_page_private {
> > + spinlock_t io_lock;
> > + unsigned long bstate[BLK_STATE_NR_LONGS];
> > +};
> > +
> > struct extent_state;
> > struct btrfs_root;
> > struct btrfs_io_bio;
> > @@ -341,8 +401,14 @@ int extent_readpages(struct extent_io_tree *tree,
> > get_extent_t get_extent);
> > int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
> > __u64 start, __u64 len, get_extent_t *get_extent);
> > -void set_page_extent_mapped(struct page *page);
> > -
> > +int set_page_extent_mapped(struct page *page);
> > +int clear_page_extent_mapped(struct page *page);
> > +int set_page_blks_state(struct page *page, unsigned long blk_states,
> > + u64 start, u64 end);
> > +int clear_page_blks_state(struct page *page, unsigned long blk_states,
> > + u64 start, u64 end);
> > +int test_page_blks_state(struct page *page, enum blk_state blk_state,
> > + u64 start, u64 end, int check_all);
> > struct extent_buffer *alloc_extent_buffer(struct btrfs_fs_info *fs_info,
> > u64 start);
> > struct extent_buffer *__alloc_dummy_extent_buffer(struct btrfs_fs_info
> > *fs_info,
> > diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> > index 833160e..27cb723 100644
> > --- a/fs/btrfs/inode.c
> > +++ b/fs/btrfs/inode.c
> > @@ -6817,7 +6817,6 @@ struct extent_map *btrfs_get_extent(struct inode
> > *inode, struct page *page,
> > struct btrfs_key found_key;
> > struct extent_map *em = NULL;
> > struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
> > - struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
> > struct btrfs_trans_handle *trans = NULL;
> > const bool new_inline = !page || create;
> >
> > @@ -6994,8 +6993,11 @@ next:
> > kunmap(page);
> > btrfs_mark_buffer_dirty(leaf);
> > }
> > - set_extent_uptodate(io_tree, em->start,
> > - extent_map_end(em) - 1, NULL, GFP_NOFS);
> > + if (root->sectorsize == PAGE_SIZE)
> > + SetPageUptodate(page);
> > + else
> > + set_page_blks_state(page, 1 << BLK_STATE_UPTODATE,
> > + em->start, extent_map_end(em) - 1);
> > goto insert;
> > }
> > not_found:
> > @@ -8800,11 +8802,9 @@ static int __btrfs_releasepage(struct page *page,
> > gfp_t gfp_flags)
> > tree = &BTRFS_I(page->mapping->host)->io_tree;
> > map = &BTRFS_I(page->mapping->host)->extent_tree;
> > ret = try_release_extent_mapping(map, tree, page, gfp_flags);
> > - if (ret == 1) {
> > - ClearPagePrivate(page);
> > - set_page_private(page, 0);
> > - put_page(page);
> > - }
> > + if (ret == 1)
> > + clear_page_extent_mapped(page);
> > +
> > return ret;
> > }
>
> Overall I'm happy with this approach, just clean up the things, split out the
> uptdate tracking with an explanation if that is really what your intent is.
> Thanks,
>
--
chandan
--
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
