On 4/15/21 1:04 AM, Qu Wenruo wrote:
The new function, submit_eb_subpage(), will submit all the dirty extent
buffers in the page.
The major difference between submit_eb_page() and submit_eb_subpage()
is:
- How to grab extent buffer
Now we use find_extent_buffer_nospinlock() other than using
page::private.
All other different handling is already done in functions like
lock_extent_buffer_for_io() and write_one_eb().
Signed-off-by: Qu Wenruo <w...@suse.com>
---
fs/btrfs/extent_io.c | 95 ++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 95 insertions(+)
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index c068c2fcba09..7d1fca9b87f0 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -4323,6 +4323,98 @@ static noinline_for_stack int write_one_eb(struct
extent_buffer *eb,
return ret;
}
+/*
+ * Submit one subpage btree page.
+ *
+ * The main difference between submit_eb_page() is:
+ * - Page locking
+ * For subpage, we don't rely on page locking at all.
+ *
+ * - Flush write bio
+ * We only flush bio if we may be unable to fit current extent buffers into
+ * current bio.
+ *
+ * Return >=0 for the number of submitted extent buffers.
+ * Return <0 for fatal error.
+ */
+static int submit_eb_subpage(struct page *page,
+ struct writeback_control *wbc,
+ struct extent_page_data *epd)
+{
+ struct btrfs_fs_info *fs_info = btrfs_sb(page->mapping->host->i_sb);
+ int submitted = 0;
+ u64 page_start = page_offset(page);
+ int bit_start = 0;
+ int nbits = BTRFS_SUBPAGE_BITMAP_SIZE;
+ int sectors_per_node = fs_info->nodesize >> fs_info->sectorsize_bits;
+ int ret;
+
+ /* Lock and write each dirty extent buffers in the range */
+ while (bit_start < nbits) {
+ struct btrfs_subpage *subpage = (struct btrfs_subpage
*)page->private;
+ struct extent_buffer *eb;
+ unsigned long flags;
+ u64 start;
+
+ /*
+ * Take private lock to ensure the subpage won't be detached
+ * halfway.
+ */
+ spin_lock(&page->mapping->private_lock);
+ if (!PagePrivate(page)) {
+ spin_unlock(&page->mapping->private_lock);
+ break;
+ }
+ spin_lock_irqsave(&subpage->lock, flags);
writepages doesn't get called with irq context, so you can just do
spin_lock_irq()/spin_unlock_irq().
+ if (!((1 << bit_start) & subpage->dirty_bitmap)) {
Can we make this a helper so it's more clear what's going on here? Thanks,
Josef
