From: Toshiyuki Okajima <toshi.okajima@xxxxxxxxxxxxxx>
Pages in the page cache belonging to ext4 data files are released via
the ext4_releasepage() function specified in the ext4 inode's
address_space_ops. However, metadata blocks (such as indirect blocks,
directory blocks, etc) are managed via the block device
address_space_ops, and they can not be released by
try_to_free_buffers() if they have a journal head attached to them.
To address this, we supply a release_metadata function which is called
by the block device's blkdev_releasepage() function, which calls
journal_try_to_free_buffers() function to free the metadata.
Signed-off-by: Toshiyuki Okajima <toshi.okajima@xxxxxxxxxxxxxx>
Signed-off-by: "Theodore Ts'o" <tytso@xxxxxxx>
Cc: linux-fsdevel@xxxxxxxxxxxxxxx
---
fs/ext4/ext4.h | 2 ++
fs/ext4/inode.c | 29 +++++++++++++++++++++++++++++
fs/ext4/super.c | 4 ++++
3 files changed, 35 insertions(+), 0 deletions(-)
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 695b45c..91e06e4 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1099,6 +1099,8 @@ extern int ext4_chunk_trans_blocks(struct inode *, int nrblocks);
extern int ext4_block_truncate_page(handle_t *handle,
struct address_space *mapping, loff_t from);
extern int ext4_page_mkwrite(struct vm_area_struct *vma, struct page *page);
+extern int ext4_release_metadata(void *client, struct page *page,
+ gfp_t wait);
/* ioctl.c */
extern long ext4_ioctl(struct file *, unsigned int, unsigned long);
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index f6d9447..1647903 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3045,6 +3045,35 @@ static int ext4_releasepage(struct page *page, gfp_t wait)
}
/*
+ * Try to release metadata pages (indirect blocks, directories) which are
+ * mapped via the block device. Since these pages could have journal heads
+ * which would prevent try_to_free_buffers() from freeing them, we must use
+ * jbd2 layer's try_to_free_buffers() function to release them.
+ *
+ * Note: we have to strip the __GFP_WAIT flag before calling
+ * jbd2_journal_try_to_free_buffers because blkdev_releasepage is
+ * called while holding a spinlock (bdev_inode.client_lock).
+ * Fortunately the metadata buffers we are interested are freed right
+ * away and do not require calling journal_wait_for_transaction_sync_data().
+ */
+int ext4_release_metadata(void *client, struct page *page, gfp_t wait)
+{
+ struct super_block *sb = (struct super_block*)client;
+ journal_t *journal;
+
+ WARN_ON(PageChecked(page));
+ if (!page_has_buffers(page))
+ return 0;
+ BUG_ON(EXT4_SB(sb) == NULL);
+ journal = EXT4_SB(sb)->s_journal;
+ if (journal != NULL)
+ return jbd2_journal_try_to_free_buffers(journal, page,
+ wait & ~__GFP_WAIT);
+ else
+ return try_to_free_buffers(page);
+}
+
+/*
* If the O_DIRECT write will extend the file then add this inode to the
* orphan list. So recovery will truncate it back to the original size
* if the machine crashes during the write.
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index bd41fad..f447c46 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -3689,6 +3689,8 @@ static struct file_system_type ext4_fs_type = {
.name = "ext4",
.get_sb = ext4_get_sb,
.kill_sb = kill_block_super,
+ .release_metadata
+ = ext4_release_metadata,
.fs_flags = FS_REQUIRES_DEV,
};
@@ -3708,6 +3710,8 @@ static struct file_system_type ext4dev_fs_type = {
.name = "ext4dev",
.get_sb = ext4dev_get_sb,
.kill_sb = kill_block_super,
+ .release_metadata
+ = ext4_release_metadata,
.fs_flags = FS_REQUIRES_DEV,
};
MODULE_ALIAS("ext4dev");
--
1.6.0.4.8.g36f27.dirty
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