diff mbox series

[v5,05/18] btrfs: make grab_extent_buffer_from_page() handle subpage case

Message ID 20210126083402.142577-6-wqu@suse.com (mailing list archive)
State New, archived
Headers show
Series btrfs: add read-only support for subpage sector size | expand

Commit Message

Qu Wenruo Jan. 26, 2021, 8:33 a.m. UTC 
For subpage case, grab_extent_buffer() can't really get an extent buffer
just from btrfs_subpage.

We have radix tree lock protecting us from inserting the same eb into
the tree.  Thus we don't really need to do the extra hassle, just let
alloc_extent_buffer() handle the existing eb in radix tree.

Now if two ebs are being allocated as the same time, one will fail with
-EEIXST when inserting into the radix tree.

So for grab_extent_buffer(), just always return NULL for subpage case.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
---
 fs/btrfs/extent_io.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

Comments

Josef Bacik Jan. 27, 2021, 4:20 p.m. UTC | #1 
On 1/26/21 3:33 AM, Qu Wenruo wrote:
> For subpage case, grab_extent_buffer() can't really get an extent buffer
> just from btrfs_subpage.
> 
> We have radix tree lock protecting us from inserting the same eb into
> the tree.  Thus we don't really need to do the extra hassle, just let
> alloc_extent_buffer() handle the existing eb in radix tree.
> 
> Now if two ebs are being allocated as the same time, one will fail with
> -EEIXST when inserting into the radix tree.
> 
> So for grab_extent_buffer(), just always return NULL for subpage case.
> 
> Signed-off-by: Qu Wenruo <wqu@suse.com>
> Reviewed-by: David Sterba <dsterba@suse.com>
> Signed-off-by: David Sterba <dsterba@suse.com>

Reviewed-by: Josef Bacik <josef@toxicpanda.com>

Thanks,

Josef
diff mbox series

Patch

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index ea105cb69e3a..16a29f63cfd1 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -5282,10 +5282,19 @@  struct extent_buffer *alloc_test_extent_buffer(struct btrfs_fs_info *fs_info,
 }
 #endif
 
-static struct extent_buffer *grab_extent_buffer(struct page *page)
+static struct extent_buffer *grab_extent_buffer(
+		struct btrfs_fs_info *fs_info, struct page *page)
 {
 	struct extent_buffer *exists;
 
+	/*
+	 * For subpage case, we completely rely on radix tree to ensure we
+	 * don't try to insert two ebs for the same bytenr.  So here we always
+	 * return NULL and just continue.
+	 */
+	if (fs_info->sectorsize < PAGE_SIZE)
+		return NULL;
+
 	/* Page not yet attached to an extent buffer */
 	if (!PagePrivate(page))
 		return NULL;
@@ -5371,7 +5380,7 @@  struct extent_buffer *alloc_extent_buffer(struct btrfs_fs_info *fs_info,
 		}
 
 		spin_lock(&mapping->private_lock);
-		exists = grab_extent_buffer(p);
+		exists = grab_extent_buffer(fs_info, p);
 		if (exists) {
 			spin_unlock(&mapping->private_lock);
 			unlock_page(p);