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btrfs: defrag: factor out page preparation into a helper

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In cluster_pages_for_defrag(), we have complex code block inside one
for() loop.

The code block is to prepare one page for defrag, this will ensure:

- The page is locked and set up properly.
- No ordered extent exists in the page range.
- The page is uptodate.

This behavior is pretty common and will be reused by later defrag
rework.

So factor out the code into its own helper, defrag_prepare_one_page(),
for later usage, and cleanup the code by a little.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Qu Wenruo 2021-08-06 16:12:35 +08:00 committed by David Sterba
parent 76068cae63
commit 5767b50c00
1 changed files with 87 additions and 61 deletions
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148
fs/btrfs/ioctl.c
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@ -1197,6 +1197,88 @@ out:
return ret;
}
/*
* Prepare one page to be defragged.
*
* This will ensure:
*
* - Returned page is locked and has been set up properly.
* - No ordered extent exists in the page.
* - The page is uptodate.
*
* NOTE: Caller should also wait for page writeback after the cluster is
* prepared, here we don't do writeback wait for each page.
*/
static struct page *defrag_prepare_one_page(struct btrfs_inode *inode,
pgoff_t index)
{
struct address_space *mapping = inode->vfs_inode.i_mapping;
gfp_t mask = btrfs_alloc_write_mask(mapping);
u64 page_start = (u64)index << PAGE_SHIFT;
u64 page_end = page_start + PAGE_SIZE - 1;
struct extent_state *cached_state = NULL;
struct page *page;
int ret;
again:
page = find_or_create_page(mapping, index, mask);
if (!page)
return ERR_PTR(-ENOMEM);
ret = set_page_extent_mapped(page);
if (ret < 0) {
unlock_page(page);
put_page(page);
return ERR_PTR(ret);
}
/* Wait for any existing ordered extent in the range */
while (1) {
struct btrfs_ordered_extent *ordered;
lock_extent_bits(&inode->io_tree, page_start, page_end, &cached_state);
ordered = btrfs_lookup_ordered_range(inode, page_start, PAGE_SIZE);
unlock_extent_cached(&inode->io_tree, page_start, page_end,
&cached_state);
if (!ordered)
break;
unlock_page(page);
btrfs_start_ordered_extent(ordered, 1);
btrfs_put_ordered_extent(ordered);
lock_page(page);
/*
* We unlocked the page above, so we need check if it was
* released or not.
*/
if (page->mapping != mapping || !PagePrivate(page)) {
unlock_page(page);
put_page(page);
goto again;
}
}
/*
* Now the page range has no ordered extent any more. Read the page to
* make it uptodate.
*/
if (!PageUptodate(page)) {
btrfs_readpage(NULL, page);
lock_page(page);
if (page->mapping != mapping || !PagePrivate(page)) {
unlock_page(page);
put_page(page);
goto again;
}
if (!PageUptodate(page)) {
unlock_page(page);
put_page(page);
return ERR_PTR(-EIO);
}
}
return page;
}
/*
* it doesn't do much good to defrag one or two pages
* at a time. This pulls in a nice chunk of pages
@ -1224,11 +1306,8 @@ static int cluster_pages_for_defrag(struct inode *inode,
int ret;
int i;
int i_done;
struct btrfs_ordered_extent *ordered;
struct extent_state *cached_state = NULL;
struct extent_io_tree *tree;
struct extent_changeset *data_reserved = NULL;
gfp_t mask = btrfs_alloc_write_mask(inode->i_mapping);
file_end = (isize - 1) >> PAGE_SHIFT;
if (!isize || start_index > file_end)
@ -1241,69 +1320,16 @@ static int cluster_pages_for_defrag(struct inode *inode,
if (ret)
return ret;
i_done = 0;
tree = &BTRFS_I(inode)->io_tree;
/* step one, lock all the pages */
for (i = 0; i < page_cnt; i++) {
struct page *page;
again:
page = find_or_create_page(inode->i_mapping,
start_index + i, mask);
if (!page)
break;
ret = set_page_extent_mapped(page);
if (ret < 0) {
unlock_page(page);
put_page(page);
page = defrag_prepare_one_page(BTRFS_I(inode), start_index + i);
if (IS_ERR(page)) {
ret = PTR_ERR(page);
break;
}
page_start = page_offset(page);
page_end = page_start + PAGE_SIZE - 1;
while (1) {
lock_extent_bits(tree, page_start, page_end,
&cached_state);
ordered = btrfs_lookup_ordered_extent(BTRFS_I(inode),
page_start);
unlock_extent_cached(tree, page_start, page_end,
&cached_state);
if (!ordered)
break;
unlock_page(page);
btrfs_start_ordered_extent(ordered, 1);
btrfs_put_ordered_extent(ordered);
lock_page(page);
/*
* we unlocked the page above, so we need check if
* it was released or not.
*/
if (page->mapping != inode->i_mapping ||
!PagePrivate(page)) {
unlock_page(page);
put_page(page);
goto again;
}
}
if (!PageUptodate(page)) {
btrfs_readpage(NULL, page);
lock_page(page);
if (!PageUptodate(page)) {
unlock_page(page);
put_page(page);
ret = -EIO;
break;
}
}
if (page->mapping != inode->i_mapping || !PagePrivate(page)) {
unlock_page(page);
put_page(page);
goto again;
}
pages[i] = page;
i_done++;
}
@ -1314,8 +1340,8 @@ again:
goto out;
/*
* so now we have a nice long stream of locked
* and up to date pages, lets wait on them
* Now we have a nice long stream of locked and up to date pages, let's
* wait on them.
*/
for (i = 0; i < i_done; i++)
wait_on_page_writeback(pages[i]);