From: Josef Bacik <josef@toxicpanda.com>
To: Qu Wenruo <wqu@suse.com>, linux-btrfs@vger.kernel.org
Cc: David Sterba <dsterba@suse.com>
Subject: Re: [PATCH v5 17/18] btrfs: integrate page status update for data read path into begin/end_page_read()
Date: Wed, 27 Jan 2021 12:13:27 -0500 [thread overview]
Message-ID: <dd190a49-9c70-c6a5-1c2d-896d290c1a76@toxicpanda.com> (raw)
In-Reply-To: <20210126083402.142577-18-wqu@suse.com>
On 1/26/21 3:34 AM, Qu Wenruo wrote:
> In btrfs data page read path, the page status update are handled in two
> different locations:
>
> btrfs_do_read_page()
> {
> while (cur <= end) {
> /* No need to read from disk */
> if (HOLE/PREALLOC/INLINE){
> memset();
> set_extent_uptodate();
> continue;
> }
> /* Read from disk */
> ret = submit_extent_page(end_bio_extent_readpage);
> }
>
> end_bio_extent_readpage()
> {
> endio_readpage_uptodate_page_status();
> }
>
> This is fine for sectorsize == PAGE_SIZE case, as for above loop we
> should only hit one branch and then exit.
>
> But for subpage, there are more works to be done in page status update:
> - Page Unlock condition
> Unlike regular page size == sectorsize case, we can no longer just
> unlock a page without a brain.
> Only the last reader of the page can unlock the page.
> This means, we can unlock the page either in the while() loop, or in
> the endio function.
>
> - Page uptodate condition
> Since we have multiple sectors to read for a page, we can only mark
> the full page uptodate if all sectors are uptodate.
>
> To handle both subpage and regular cases, introduce a pair of functions
> to help handling page status update:
>
> - being_page_read()
> For regular case, it does nothing.
> For subpage case, it update the reader counters so that later
> end_page_read() can know who is the last one to unlock the page.
>
> - end_page_read()
> This is just endio_readpage_uptodate_page_status() renamed.
> The original name is a little too long and too specific for endio.
>
> The only new trick added is the condition for page unlock.
> Now for subage data, we unlock the page if we're the last reader.
>
> This does not only provide the basis for subpage data read, but also
> hide the special handling of page read from the main read loop.
>
> Signed-off-by: Qu Wenruo <wqu@suse.com>
> Signed-off-by: David Sterba <dsterba@suse.com>
> ---
> fs/btrfs/extent_io.c | 38 ++++++++++++++++++++----------
> fs/btrfs/subpage.c | 56 ++++++++++++++++++++++++++++++++++----------
> fs/btrfs/subpage.h | 8 +++++++
> 3 files changed, 78 insertions(+), 24 deletions(-)
>
> diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
> index eeee3213daaa..7fc2c62d4eb9 100644
> --- a/fs/btrfs/extent_io.c
> +++ b/fs/btrfs/extent_io.c
> @@ -2839,8 +2839,17 @@ static void endio_readpage_release_extent(struct processed_extent *processed,
> processed->uptodate = uptodate;
> }
>
> -static void endio_readpage_update_page_status(struct page *page, bool uptodate,
> - u64 start, u32 len)
> +static void begin_data_page_read(struct btrfs_fs_info *fs_info, struct page *page)
> +{
> + ASSERT(PageLocked(page));
> + if (fs_info->sectorsize == PAGE_SIZE)
> + return;
> +
> + ASSERT(PagePrivate(page));
> + btrfs_subpage_start_reader(fs_info, page, page_offset(page), PAGE_SIZE);
> +}
> +
> +static void end_page_read(struct page *page, bool uptodate, u64 start, u32 len)
> {
> struct btrfs_fs_info *fs_info = btrfs_sb(page->mapping->host->i_sb);
>
> @@ -2856,7 +2865,12 @@ static void endio_readpage_update_page_status(struct page *page, bool uptodate,
>
> if (fs_info->sectorsize == PAGE_SIZE)
> unlock_page(page);
> - /* Subpage locking will be handled in later patches */
> + 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.
> + */
> + btrfs_subpage_end_reader(fs_info, page, start, len);
> }
>
> /*
> @@ -2993,7 +3007,7 @@ static void end_bio_extent_readpage(struct bio *bio)
> bio_offset += len;
>
> /* Update page status and unlock */
> - endio_readpage_update_page_status(page, uptodate, start, len);
> + end_page_read(page, uptodate, start, len);
> endio_readpage_release_extent(&processed, BTRFS_I(inode),
> start, end, uptodate);
> }
> @@ -3263,6 +3277,7 @@ int btrfs_do_readpage(struct page *page, struct extent_map **em_cached,
> unsigned int read_flags, u64 *prev_em_start)
> {
> struct inode *inode = page->mapping->host;
> + struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
> u64 start = page_offset(page);
> const u64 end = start + PAGE_SIZE - 1;
> u64 cur = start;
> @@ -3306,6 +3321,7 @@ int btrfs_do_readpage(struct page *page, struct extent_map **em_cached,
> kunmap_atomic(userpage);
> }
> }
You have two error cases above this
ret = set_page_extent_mapped(page);
if (ret < 0) {
unlock_extent(tree, start, end);
SetPageError(page);
goto out;
}
and
if (!PageUptodate(page)) {
if (cleancache_get_page(page) == 0) {
BUG_ON(blocksize != PAGE_SIZE);
unlock_extent(tree, start, end);
goto out;
}
}
which will now leave the page locked when it errors out. Not to mention I'm
pretty sure you want to use btrfs_page_set_error() instead of SetPageError() in
that first case.
> + begin_data_page_read(fs_info, page);
> while (cur <= end) {
> bool force_bio_submit = false;
> u64 disk_bytenr;
> @@ -3323,13 +3339,14 @@ int btrfs_do_readpage(struct page *page, struct extent_map **em_cached,
> &cached, GFP_NOFS);
> unlock_extent_cached(tree, cur,
> cur + iosize - 1, &cached);
> + end_page_read(page, true, cur, iosize);
> break;
> }
> em = __get_extent_map(inode, page, pg_offset, cur,
> end - cur + 1, em_cached);
> if (IS_ERR_OR_NULL(em)) {
> - SetPageError(page);
> unlock_extent(tree, cur, end);
> + end_page_read(page, false, cur, end + 1 - cur);
> break;
> }
> extent_offset = cur - em->start;
> @@ -3412,6 +3429,7 @@ int btrfs_do_readpage(struct page *page, struct extent_map **em_cached,
> &cached, GFP_NOFS);
> unlock_extent_cached(tree, cur,
> cur + iosize - 1, &cached);
> + end_page_read(page, true, cur, iosize);
> cur = cur + iosize;
> pg_offset += iosize;
> continue;
> @@ -3421,6 +3439,7 @@ int btrfs_do_readpage(struct page *page, struct extent_map **em_cached,
> EXTENT_UPTODATE, 1, NULL)) {
> check_page_uptodate(tree, page);
> unlock_extent(tree, cur, cur + iosize - 1);
> + end_page_read(page, true, cur, iosize);
> cur = cur + iosize;
> pg_offset += iosize;
> continue;
> @@ -3429,8 +3448,8 @@ int btrfs_do_readpage(struct page *page, struct extent_map **em_cached,
> * to date. Error out
> */
> if (block_start == EXTENT_MAP_INLINE) {
> - SetPageError(page);
> unlock_extent(tree, cur, cur + iosize - 1);
> + end_page_read(page, false, cur, iosize);
> cur = cur + iosize;
> pg_offset += iosize;
> continue;
> @@ -3447,19 +3466,14 @@ int btrfs_do_readpage(struct page *page, struct extent_map **em_cached,
> nr++;
> *bio_flags = this_bio_flag;
> } else {
> - SetPageError(page);
> unlock_extent(tree, cur, cur + iosize - 1);
> + end_page_read(page, false, cur, iosize);
> goto out;
> }
> cur = cur + iosize;
> pg_offset += iosize;
> }
> out:
> - if (!nr) {
> - if (!PageError(page))
> - SetPageUptodate(page);
> - unlock_page(page);
> - }
We can just delete out: here and either return on error or break from the main
loop. Thanks,
Josef
next prev parent reply other threads:[~2021-01-27 17:15 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-26 8:33 [PATCH v5 00/18] btrfs: add read-only support for subpage sector size Qu Wenruo
2021-01-26 8:33 ` [PATCH v5 01/18] btrfs: merge PAGE_CLEAR_DIRTY and PAGE_SET_WRITEBACK to PAGE_START_WRITEBACK Qu Wenruo
2021-01-27 15:56 ` Josef Bacik
2021-01-26 8:33 ` [PATCH v5 02/18] btrfs: set UNMAPPED bit early in btrfs_clone_extent_buffer() for subpage support Qu Wenruo
2021-01-27 15:56 ` Josef Bacik
2021-01-26 8:33 ` [PATCH v5 03/18] btrfs: introduce the skeleton of btrfs_subpage structure Qu Wenruo
2021-01-26 8:33 ` [PATCH v5 04/18] btrfs: make attach_extent_buffer_page() handle subpage case Qu Wenruo
2021-01-27 16:01 ` Josef Bacik
2021-01-26 8:33 ` [PATCH v5 05/18] btrfs: make grab_extent_buffer_from_page() " Qu Wenruo
2021-01-27 16:20 ` Josef Bacik
2021-01-26 8:33 ` [PATCH v5 06/18] btrfs: support subpage for extent buffer page release Qu Wenruo
2021-01-27 16:21 ` Josef Bacik
2021-02-01 15:32 ` David Sterba
2021-01-26 8:33 ` [PATCH v5 07/18] btrfs: attach private to dummy extent buffer pages Qu Wenruo
2021-01-27 16:21 ` Josef Bacik
2021-01-26 8:33 ` [PATCH v5 08/18] btrfs: introduce helpers for subpage uptodate status Qu Wenruo
2021-01-27 16:34 ` Josef Bacik
2021-01-26 8:33 ` [PATCH v5 09/18] btrfs: introduce helpers for subpage error status Qu Wenruo
2021-01-27 16:34 ` Josef Bacik
2021-01-26 8:33 ` [PATCH v5 10/18] btrfs: support subpage in set/clear_extent_buffer_uptodate() Qu Wenruo
2021-01-27 16:35 ` Josef Bacik
2021-01-26 8:33 ` [PATCH v5 11/18] btrfs: support subpage in btrfs_clone_extent_buffer Qu Wenruo
2021-01-27 16:35 ` Josef Bacik
2021-01-26 8:33 ` [PATCH v5 12/18] btrfs: support subpage in try_release_extent_buffer() Qu Wenruo
2021-01-27 16:37 ` Josef Bacik
2021-01-26 8:33 ` [PATCH v5 13/18] btrfs: introduce read_extent_buffer_subpage() Qu Wenruo
2021-01-27 16:39 ` Josef Bacik
2021-01-26 8:33 ` [PATCH v5 14/18] btrfs: support subpage in endio_readpage_update_page_status() Qu Wenruo
2021-01-27 16:42 ` Josef Bacik
2021-01-26 8:33 ` [PATCH v5 15/18] btrfs: introduce subpage metadata validation check Qu Wenruo
2021-01-27 16:47 ` Josef Bacik
2021-01-26 8:34 ` [PATCH v5 16/18] btrfs: introduce btrfs_subpage for data inodes Qu Wenruo
2021-01-27 16:56 ` Josef Bacik
2021-02-01 15:42 ` David Sterba
2021-01-26 8:34 ` [PATCH v5 17/18] btrfs: integrate page status update for data read path into begin/end_page_read() Qu Wenruo
2021-01-27 17:13 ` Josef Bacik [this message]
2021-02-01 15:47 ` David Sterba
2021-01-26 8:34 ` [PATCH v5 18/18] btrfs: allow RO mount of 4K sector size fs on 64K page system Qu Wenruo
2021-01-27 17:13 ` Josef Bacik
2021-02-01 15:49 ` David Sterba
2021-01-27 16:17 ` [PATCH v5 00/18] btrfs: add read-only support for subpage sector size Josef Bacik
2021-01-28 0:30 ` Qu Wenruo
2021-01-28 10:34 ` David Sterba
2021-01-28 10:51 ` Qu Wenruo
2021-02-01 14:50 ` David Sterba
2021-02-01 15:55 ` David Sterba
2021-02-02 9:21 ` [bug report] Unable to handle kernel paging request Anand Jain
2021-02-02 10:23 ` Qu Wenruo
2021-02-02 11:28 ` Anand Jain
2021-02-02 13:37 ` Anand Jain
2021-02-04 5:13 ` Qu Wenruo
2021-02-03 13:20 ` [PATCH v5 00/18] btrfs: add read-only support for subpage sector size David Sterba
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