The 'struct ext4_journalled_wb_page' is a journal callback entry;
use 'kmem_cache ext4_journalled_wb_page_cachep' to alloc/free it.
It will be used to end page writeback on transaction commit,
only for writeback of mmaped pagecache in data=journal mode
(i.e., ext4_writepage() -> __ext4_journalled_writepage()).
The next patch will add the associated set page writeback
and add the callback entry to the list in the transaction;
and process that list in the ext4 journal commit callback.
This builds on top of the existing journal commit callback
functions (not used anymore), using t_private_list in jbd2.
(introduced with commit 18aadd47f884 ("ext4: expand commit
callback and"), and not used in commit a015434480dc ("ext4:
send parallel discards on commit completions").)
P.S.: ext4_journal_commit_callback() does have spinlocking
with s_md_lock that is not needed for this particular case
(which seems to be the only one), as it has no concurrency
on transaction commit time/only during transaction running
time (currently only done in __ext4_journalled_writepage()).
But no changes for now, just keep it as it is/has been, so
it remains general in case other usages arise that need it.
Signed-off-by: Mauricio Faria de Oliveira <mfo@xxxxxxxxxxxxx>
---
fs/ext4/ext4_jbd2.h | 16 ++++++++++++++++
fs/ext4/page-io.c | 11 +++++++++++
2 files changed, 27 insertions(+)
diff --git a/fs/ext4/ext4_jbd2.h b/fs/ext4/ext4_jbd2.h
index 4b9002f0e84c..9ea8ee583931 100644
--- a/fs/ext4/ext4_jbd2.h
+++ b/fs/ext4/ext4_jbd2.h
@@ -209,6 +209,22 @@ static inline bool ext4_journal_callback_try_del(handle_t *handle,
return deleted;
}
+/* The struct ext4_journalled_wb_page is a journal callback entry to
+ * end page writeback on transaction commit in the data=journal mode.
+ *
+ * This is used for writeback of mmaped pagecache in data=journal mode
+ * (see ext4_writepage() -> __ext4_journalled_writepage() for details.)
+ */
+struct ext4_journalled_wb_page {
+ /* First member must be the journal callback entry */
+ struct ext4_journal_cb_entry ejwp_jce;
+
+ /* Pointer to page marked for writeback */
+ struct page *ejwp_page;
+};
+
+extern struct kmem_cache *ext4_journalled_wb_page_cachep;
+
int
ext4_mark_iloc_dirty(handle_t *handle,
struct inode *inode,
diff --git a/fs/ext4/page-io.c b/fs/ext4/page-io.c
index de6fe969f773..67fabeef6bf2 100644
--- a/fs/ext4/page-io.c
+++ b/fs/ext4/page-io.c
@@ -32,6 +32,7 @@
static struct kmem_cache *io_end_cachep;
static struct kmem_cache *io_end_vec_cachep;
+struct kmem_cache *ext4_journalled_wb_page_cachep;
int __init ext4_init_pageio(void)
{
@@ -44,6 +45,15 @@ int __init ext4_init_pageio(void)
kmem_cache_destroy(io_end_cachep);
return -ENOMEM;
}
+
+ ext4_journalled_wb_page_cachep = KMEM_CACHE(ext4_journalled_wb_page,
+ SLAB_RECLAIM_ACCOUNT);
+ if (ext4_journalled_wb_page_cachep == NULL) {
+ kmem_cache_destroy(io_end_cachep);
+ kmem_cache_destroy(io_end_vec_cachep);
+ return -ENOMEM;
+ }
+
return 0;
}
@@ -51,6 +61,7 @@ void ext4_exit_pageio(void)
{
kmem_cache_destroy(io_end_cachep);
kmem_cache_destroy(io_end_vec_cachep);
+ kmem_cache_destroy(ext4_journalled_wb_page_cachep);
}
struct ext4_io_end_vec *ext4_alloc_io_end_vec(ext4_io_end_t *io_end)
--
2.20.1
