The documentation for this function has become separated from it over
time; move it to the right place and turn it into kernel-doc. Mild
editing of the content to make it more about what the function does, and
less about how it does it.
Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
---
fs/buffer.c | 44 ++++++++++++++++++++++++--------------------
1 file changed, 24 insertions(+), 20 deletions(-)
diff --git a/fs/buffer.c b/fs/buffer.c
index 31e171382e00..a657920802ac 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -2863,26 +2863,6 @@ int sync_dirty_buffer(struct buffer_head *bh)
}
EXPORT_SYMBOL(sync_dirty_buffer);
-/*
- * try_to_free_buffers() checks if all the buffers on this particular folio
- * are unused, and releases them if so.
- *
- * Exclusion against try_to_free_buffers may be obtained by either
- * locking the folio or by holding its mapping's private_lock.
- *
- * If the folio is dirty but all the buffers are clean then we need to
- * be sure to mark the folio clean as well. This is because the folio
- * may be against a block device, and a later reattachment of buffers
- * to a dirty folio will set *all* buffers dirty. Which would corrupt
- * filesystem data on the same device.
- *
- * The same applies to regular filesystem folios: if all the buffers are
- * clean then we set the folio clean and proceed. To do that, we require
- * total exclusion from block_dirty_folio(). That is obtained with
- * private_lock.
- *
- * try_to_free_buffers() is non-blocking.
- */
static inline int buffer_busy(struct buffer_head *bh)
{
return atomic_read(&bh->b_count) |
@@ -2916,6 +2896,30 @@ drop_buffers(struct folio *folio, struct buffer_head **buffers_to_free)
return false;
}
+/**
+ * try_to_free_buffers: Release buffers attached to this folio.
+ * @folio: The folio.
+ *
+ * If any buffers are in use (dirty, under writeback, elevated refcount),
+ * no buffers will be freed.
+ *
+ * If the folio is dirty but all the buffers are clean then we need to
+ * be sure to mark the folio clean as well. This is because the folio
+ * may be against a block device, and a later reattachment of buffers
+ * to a dirty folio will set *all* buffers dirty. Which would corrupt
+ * filesystem data on the same device.
+ *
+ * The same applies to regular filesystem folios: if all the buffers are
+ * clean then we set the folio clean and proceed. To do that, we require
+ * total exclusion from block_dirty_folio(). That is obtained with
+ * private_lock.
+ *
+ * Exclusion against try_to_free_buffers may be obtained by either
+ * locking the folio or by holding its mapping's private_lock.
+ *
+ * Context: Process context. @folio must be locked. Will not sleep.
+ * Return: true if all buffers attached to this folio were freed.
+ */
bool try_to_free_buffers(struct folio *folio)
{
struct address_space * const mapping = folio->mapping;
--
2.43.0
