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Btrfs: set page->private to the eb
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We spend a lot of time looking up extent buffers from pages when we could just
store the pointer to the eb the page is associated with in page->private.  This
patch does just that, and it makes things a little simpler and reduces a bit of
CPU overhead involved with doing metadata IO.  Thanks,

Signed-off-by: Josef Bacik <josef@redhat.com>
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Josef Bacik authored and Chris Mason committed Mar 26, 2012
1 parent 727011e commit 4f2de97
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Showing 3 changed files with 91 additions and 93 deletions.
91 changes: 23 additions & 68 deletions fs/btrfs/disk-io.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -403,39 +403,28 @@ static int csum_dirty_buffer(struct btrfs_root *root, struct page *page)
struct extent_io_tree *tree;
u64 start = (u64)page->index << PAGE_CACHE_SHIFT;
u64 found_start;
unsigned long len;
struct extent_buffer *eb;

tree = &BTRFS_I(page->mapping->host)->io_tree;

if (page->private == EXTENT_PAGE_PRIVATE)
goto out;
if (!page->private) {
WARN_ON(1);
goto out;
}
len = page->private >> 2;
WARN_ON(len == 0);

eb = find_extent_buffer(tree, start, len);
eb = (struct extent_buffer *)page->private;
if (page != eb->pages[0])
return 0;

found_start = btrfs_header_bytenr(eb);
if (found_start != start) {
WARN_ON(1);
goto err;
return 0;
}
if (eb->pages[0] != page) {
WARN_ON(1);
goto err;
return 0;
}
if (!PageUptodate(page)) {
WARN_ON(1);
goto err;
return 0;
}
csum_tree_block(root, eb, 0);
err:
free_extent_buffer(eb);
out:
return 0;
}

Expand Down Expand Up @@ -566,7 +555,6 @@ static int btree_readpage_end_io_hook(struct page *page, u64 start, u64 end,
struct extent_io_tree *tree;
u64 found_start;
int found_level;
unsigned long len;
struct extent_buffer *eb;
struct btrfs_root *root = BTRFS_I(page->mapping->host)->root;
int ret = 0;
Expand All @@ -576,13 +564,8 @@ static int btree_readpage_end_io_hook(struct page *page, u64 start, u64 end,
goto out;

tree = &BTRFS_I(page->mapping->host)->io_tree;
len = page->private >> 2;
eb = (struct extent_buffer *)page->private;

eb = find_eb_for_page(tree, page, max(root->leafsize, root->nodesize));
if (!eb) {
ret = -EIO;
goto out;
}
reads_done = atomic_dec_and_test(&eb->pages_reading);
if (!reads_done)
goto err;
Expand Down Expand Up @@ -631,7 +614,6 @@ static int btree_readpage_end_io_hook(struct page *page, u64 start, u64 end,

if (ret && eb)
clear_extent_buffer_uptodate(tree, eb, NULL);
free_extent_buffer(eb);
out:
return ret;
}
Expand All @@ -640,31 +622,17 @@ static int btree_io_failed_hook(struct bio *failed_bio,
struct page *page, u64 start, u64 end,
int mirror_num, struct extent_state *state)
{
struct extent_io_tree *tree;
unsigned long len;
struct extent_buffer *eb;
struct btrfs_root *root = BTRFS_I(page->mapping->host)->root;

tree = &BTRFS_I(page->mapping->host)->io_tree;
if (page->private == EXTENT_PAGE_PRIVATE)
goto out;
if (!page->private)
goto out;

len = page->private >> 2;
WARN_ON(len == 0);

eb = alloc_extent_buffer(tree, start, len);
if (eb == NULL)
goto out;
eb = (struct extent_buffer *)page->private;
if (page != eb->pages[0])
return -EIO;

if (test_bit(EXTENT_BUFFER_READAHEAD, &eb->bflags)) {
clear_bit(EXTENT_BUFFER_READAHEAD, &eb->bflags);
btree_readahead_hook(root, eb, eb->start, -EIO);
}
free_extent_buffer(eb);

out:
return -EIO; /* we fixed nothing */
}

Expand Down Expand Up @@ -955,10 +923,8 @@ static int btree_readpage(struct file *file, struct page *page)

static int btree_releasepage(struct page *page, gfp_t gfp_flags)
{
struct extent_io_tree *tree;
struct extent_map_tree *map;
struct extent_buffer *eb;
struct btrfs_root *root;
struct extent_io_tree *tree;
int ret;

if (PageWriteback(page) || PageDirty(page))
Expand All @@ -967,13 +933,6 @@ static int btree_releasepage(struct page *page, gfp_t gfp_flags)
tree = &BTRFS_I(page->mapping->host)->io_tree;
map = &BTRFS_I(page->mapping->host)->extent_tree;

root = BTRFS_I(page->mapping->host)->root;
if (page->private == EXTENT_PAGE_PRIVATE) {
eb = find_eb_for_page(tree, page, max(root->leafsize, root->nodesize));
free_extent_buffer(eb);
if (eb)
return 0;
}
/*
* We need to mask out eg. __GFP_HIGHMEM and __GFP_DMA32 as we're doing
* slab allocation from alloc_extent_state down the callchain where
Expand All @@ -985,14 +944,7 @@ static int btree_releasepage(struct page *page, gfp_t gfp_flags)
if (!ret)
return 0;

ret = try_release_extent_buffer(tree, page);
if (ret == 1) {
ClearPagePrivate(page);
set_page_private(page, 0);
page_cache_release(page);
}

return ret;
return try_release_extent_buffer(tree, page);
}

static void btree_invalidatepage(struct page *page, unsigned long offset)
Expand Down Expand Up @@ -3219,17 +3171,21 @@ static int btree_lock_page_hook(struct page *page, void *data,
{
struct inode *inode = page->mapping->host;
struct btrfs_root *root = BTRFS_I(inode)->root;
struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
struct extent_buffer *eb;
unsigned long len;
u64 bytenr = page_offset(page);

if (page->private == EXTENT_PAGE_PRIVATE)
/*
* We culled this eb but the page is still hanging out on the mapping,
* carry on.
*/
if (!PagePrivate(page))
goto out;

len = page->private >> 2;
eb = find_extent_buffer(io_tree, bytenr, len);
if (!eb)
eb = (struct extent_buffer *)page->private;
if (!eb) {
WARN_ON(1);
goto out;
}
if (page != eb->pages[0])
goto out;

if (!btrfs_try_tree_write_lock(eb)) {
Expand All @@ -3248,7 +3204,6 @@ static int btree_lock_page_hook(struct page *page, void *data,
}

btrfs_tree_unlock(eb);
free_extent_buffer(eb);
out:
if (!trylock_page(page)) {
flush_fn(data);
Expand Down
92 changes: 67 additions & 25 deletions fs/btrfs/extent_io.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -2473,19 +2473,24 @@ static int submit_extent_page(int rw, struct extent_io_tree *tree,
return ret;
}

void set_page_extent_mapped(struct page *page)
void attach_extent_buffer_page(struct extent_buffer *eb, struct page *page)
{
if (!PagePrivate(page)) {
SetPagePrivate(page);
page_cache_get(page);
set_page_private(page, EXTENT_PAGE_PRIVATE);
set_page_private(page, (unsigned long)eb);
} else {
WARN_ON(page->private != (unsigned long)eb);
}
}

static void set_page_extent_head(struct page *page, unsigned long len)
void set_page_extent_mapped(struct page *page)
{
WARN_ON(!PagePrivate(page));
set_page_private(page, EXTENT_PAGE_PRIVATE_FIRST_PAGE | len << 2);
if (!PagePrivate(page)) {
SetPagePrivate(page);
page_cache_get(page);
set_page_private(page, EXTENT_PAGE_PRIVATE);
}
}

/*
Expand Down Expand Up @@ -3585,6 +3590,7 @@ static struct extent_buffer *__alloc_extent_buffer(struct extent_io_tree *tree,
return NULL;
eb->start = start;
eb->len = len;
eb->tree = tree;
rwlock_init(&eb->lock);
atomic_set(&eb->write_locks, 0);
atomic_set(&eb->read_locks, 0);
Expand Down Expand Up @@ -3637,8 +3643,31 @@ static void btrfs_release_extent_buffer_page(struct extent_buffer *eb,
do {
index--;
page = extent_buffer_page(eb, index);
if (page)
if (page) {
spin_lock(&page->mapping->private_lock);
/*
* We do this since we'll remove the pages after we've
* removed the eb from the radix tree, so we could race
* and have this page now attached to the new eb. So
* only clear page_private if it's still connected to
* this eb.
*/
if (PagePrivate(page) &&
page->private == (unsigned long)eb) {
/*
* We need to make sure we haven't be attached
* to a new eb.
*/
ClearPagePrivate(page);
set_page_private(page, 0);
/* One for the page private */
page_cache_release(page);
}
spin_unlock(&page->mapping->private_lock);

/* One for when we alloced the page */
page_cache_release(page);
}
} while (index != start_idx);
}

Expand Down Expand Up @@ -3683,6 +3712,32 @@ struct extent_buffer *alloc_extent_buffer(struct extent_io_tree *tree,
WARN_ON(1);
goto free_eb;
}

spin_lock(&mapping->private_lock);
if (PagePrivate(p)) {
/*
* We could have already allocated an eb for this page
* and attached one so lets see if we can get a ref on
* the existing eb, and if we can we know it's good and
* we can just return that one, else we know we can just
* overwrite page->private.
*/
exists = (struct extent_buffer *)p->private;
if (atomic_inc_not_zero(&exists->refs)) {
spin_unlock(&mapping->private_lock);
unlock_page(p);
goto free_eb;
}

/*
* Do this so attach doesn't complain and we need to
* drop the ref the old guy had.
*/
ClearPagePrivate(p);
page_cache_release(p);
}
attach_extent_buffer_page(eb, p);
spin_unlock(&mapping->private_lock);
mark_page_accessed(p);
eb->pages[i] = p;
if (!PageUptodate(p))
Expand All @@ -3705,7 +3760,6 @@ struct extent_buffer *alloc_extent_buffer(struct extent_io_tree *tree,
if (ret == -EEXIST) {
exists = radix_tree_lookup(&tree->buffer,
start >> PAGE_CACHE_SHIFT);
/* add one reference for the caller */
atomic_inc(&exists->refs);
spin_unlock(&tree->buffer_lock);
radix_tree_preload_end();
Expand All @@ -3725,12 +3779,9 @@ struct extent_buffer *alloc_extent_buffer(struct extent_io_tree *tree,
* after the extent buffer is in the radix tree so
* it doesn't get lost
*/
set_page_extent_mapped(eb->pages[0]);
set_page_extent_head(eb->pages[0], eb->len);
SetPageChecked(eb->pages[0]);
for (i = 1; i < num_pages; i++) {
p = extent_buffer_page(eb, i);
set_page_extent_mapped(p);
ClearPageChecked(p);
unlock_page(p);
}
Expand Down Expand Up @@ -3794,10 +3845,6 @@ int clear_extent_buffer_dirty(struct extent_io_tree *tree,
lock_page(page);
WARN_ON(!PagePrivate(page));

set_page_extent_mapped(page);
if (i == 0)
set_page_extent_head(page, eb->len);

clear_page_dirty_for_io(page);
spin_lock_irq(&page->mapping->tree_lock);
if (!PageDirty(page)) {
Expand Down Expand Up @@ -4010,9 +4057,6 @@ int read_extent_buffer_pages(struct extent_io_tree *tree,
atomic_set(&eb->pages_reading, num_reads);
for (i = start_i; i < num_pages; i++) {
page = extent_buffer_page(eb, i);
set_page_extent_mapped(page);
if (i == 0)
set_page_extent_head(page, eb->len);
if (!PageUptodate(page)) {
ClearPageError(page);
err = __extent_read_full_page(tree, page,
Expand Down Expand Up @@ -4395,22 +4439,19 @@ static inline void btrfs_release_extent_buffer_rcu(struct rcu_head *head)
struct extent_buffer *eb =
container_of(head, struct extent_buffer, rcu_head);

btrfs_release_extent_buffer(eb);
__free_extent_buffer(eb);
}

int try_release_extent_buffer(struct extent_io_tree *tree, struct page *page)
{
u64 start = page_offset(page);
struct extent_buffer *eb;
struct extent_buffer *eb = (struct extent_buffer *)page->private;
int ret = 1;

spin_lock(&tree->buffer_lock);
eb = radix_tree_lookup(&tree->buffer, start >> PAGE_CACHE_SHIFT);
if (!eb) {
spin_unlock(&tree->buffer_lock);
return ret;
}
if (!PagePrivate(page) || !eb)
return 1;

spin_lock(&tree->buffer_lock);
if (atomic_read(&eb->refs) > 1 ||
test_bit(EXTENT_BUFFER_DIRTY, &eb->bflags)) {
ret = 0;
Expand All @@ -4426,6 +4467,7 @@ int try_release_extent_buffer(struct extent_io_tree *tree, struct page *page)
goto out;
}
radix_tree_delete(&tree->buffer, start >> PAGE_CACHE_SHIFT);
btrfs_release_extent_buffer_page(eb, 0);
out:
spin_unlock(&tree->buffer_lock);

Expand Down
1 change: 1 addition & 0 deletions fs/btrfs/extent_io.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -127,6 +127,7 @@ struct extent_buffer {
unsigned long map_start;
unsigned long map_len;
unsigned long bflags;
struct extent_io_tree *tree;
atomic_t refs;
atomic_t pages_reading;
struct list_head leak_list;
Expand Down

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