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Message-Id: <20200910193127.276214-4-mfo@canonical.com>
Date: Thu, 10 Sep 2020 16:31:27 -0300
From: Mauricio Faria de Oliveira <mfo@...onical.com>
To: Jan Kara <jack@...e.cz>
Cc: linux-ext4@...r.kernel.org,
dann frazier <dann.frazier@...onical.com>,
Mauricio Faria de Oliveira <mauricio.foliveira@...il.com>
Subject: [RFC PATCH v3 3/3] ext4: data=journal: write-protect pages on j_submit_inode_data_buffers()
This implements journal callbacks j_submit|finish_inode_data_buffers()
with different behavior for data=journal: to write-protect pages under
commit, preventing changes to buffers writeably mapped to userspace.
If a buffer's content changes between commit's checksum calculation
and write-out to disk, it can cause journal recovery/mount failures
upon a kernel crash or power loss.
[ 27.334874] EXT4-fs: Warning: mounting with data=journal disables delayed allocation, dioread_nolock, and O_DIRECT support!
[ 27.339492] JBD2: Invalid checksum recovering data block 8705 in log
[ 27.342716] JBD2: recovery failed
[ 27.343316] EXT4-fs (loop0): error loading journal
mount: /ext4: can't read superblock on /dev/loop0.
In j_submit_inode_data_buffers() we write-protect the inode's pages
with write_cache_pages() and redirty w/ writepage callback if needed.
In j_finish_inode_data_buffers() there is nothing do to.
And in order to use the callbacks, inodes are added to the inode list
in transaction in __ext4_journalled_writepage() and ext4_page_mkwrite().
In ext4_page_mkwrite() we must make sure that:
1) the inode is always added to the list;
thus we skip the 'all buffers mapped' optimization on data=journal;
2) the buffers are attached to transaction as dirty;
as already done in __ext4_journalled_writepage().
Signed-off-by: Mauricio Faria de Oliveira <mfo@...onical.com>
Suggested-by: Jan Kara <jack@...e.cz>
Reported-by: Dann Frazier <dann.frazier@...onical.com>
---
fs/ext4/inode.c | 29 ++++++++++++++------
fs/ext4/super.c | 72 +++++++++++++++++++++++++++++++++++++++++++++++--
2 files changed, 91 insertions(+), 10 deletions(-)
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index bf596467c234..fa4109da056c 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -1910,6 +1910,9 @@ static int __ext4_journalled_writepage(struct page *page,
err = ext4_walk_page_buffers(handle, page_bufs, 0, len, NULL,
write_end_fn);
}
+ if (ret == 0)
+ ret = err;
+ err = ext4_jbd2_inode_add_write(handle, inode, 0, len);
if (ret == 0)
ret = err;
EXT4_I(inode)->i_datasync_tid = handle->h_transaction->t_tid;
@@ -6004,9 +6007,12 @@ vm_fault_t ext4_page_mkwrite(struct vm_fault *vmf)
len = PAGE_SIZE;
/*
* Return if we have all the buffers mapped. This avoids the need to do
- * journal_start/journal_stop which can block and take a long time
+ * journal_start/journal_stop which can block and take a long time.
+ *
+ * This cannot be done for data journalling, as we have to add the
+ * inode to the transaction's list to writeprotect pages on commit.
*/
- if (page_has_buffers(page)) {
+ if (page_has_buffers(page) && !ext4_should_journal_data(inode)) {
if (!ext4_walk_page_buffers(NULL, page_buffers(page),
0, len, NULL,
ext4_bh_unmapped)) {
@@ -6032,12 +6038,14 @@ vm_fault_t ext4_page_mkwrite(struct vm_fault *vmf)
err = block_page_mkwrite(vma, vmf, get_block);
if (!err && ext4_should_journal_data(inode)) {
if (ext4_walk_page_buffers(handle, page_buffers(page), 0,
- PAGE_SIZE, NULL, do_journal_get_write_access)) {
- unlock_page(page);
- ret = VM_FAULT_SIGBUS;
- ext4_journal_stop(handle);
- goto out;
- }
+ PAGE_SIZE, NULL, do_journal_get_write_access))
+ goto out_err;
+ /* Make sure buffers are attached to the transaction as dirty */
+ if (ext4_walk_page_buffers(handle, page_buffers(page), 0,
+ PAGE_SIZE, NULL, write_end_fn))
+ goto out_err;
+ if (ext4_jbd2_inode_add_write(handle, inode, 0, PAGE_SIZE))
+ goto out_err;
ext4_set_inode_state(inode, EXT4_STATE_JDATA);
}
ext4_journal_stop(handle);
@@ -6049,6 +6057,11 @@ vm_fault_t ext4_page_mkwrite(struct vm_fault *vmf)
up_read(&EXT4_I(inode)->i_mmap_sem);
sb_end_pagefault(inode->i_sb);
return ret;
+out_err:
+ unlock_page(page);
+ ret = VM_FAULT_SIGBUS;
+ ext4_journal_stop(handle);
+ goto out;
}
vm_fault_t ext4_filemap_fault(struct vm_fault *vmf)
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 7303839d7ad9..528b5e20b71c 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -472,14 +472,82 @@ static void ext4_journal_commit_callback(journal_t *journal, transaction_t *txn)
spin_unlock(&sbi->s_md_lock);
}
+/*
+ * This writepage callback for write_cache_pages()
+ * takes care of a few cases after page cleaning.
+ *
+ * write_cache_pages() already checks for dirty pages
+ * and calls clear_page_dirty_for_io(), which we want,
+ * to write protect the pages.
+ *
+ * However, we have to redirty a page in these cases:
+ * 1) some buffer is dirty (needs checkpointing)
+ * 2) some buffer is not part of the committing transaction
+ * 3) some buffer already has b_next_transaction set
+ */
+
+static int ext4_journalled_writepage_callback(struct page *page,
+ struct writeback_control *wbc,
+ void *data)
+{
+ transaction_t *transaction = (transaction_t *) data;
+ struct buffer_head *bh, *head;
+ struct journal_head *jh;
+
+ bh = head = page_buffers(page);
+ do {
+ jh = bh2jh(bh);
+ if (buffer_dirty(bh) ||
+ (jh && (jh->b_transaction != transaction ||
+ jh->b_next_transaction))) {
+ redirty_page_for_writepage(wbc, page);
+ goto out;
+ }
+ } while ((bh = bh->b_this_page) != head);
+
+out:
+ return AOP_WRITEPAGE_ACTIVATE;
+}
+
+static int ext4_journalled_submit_inode_data_buffers(struct jbd2_inode *jinode)
+{
+ struct address_space *mapping = jinode->i_vfs_inode->i_mapping;
+ transaction_t *transaction = jinode->i_transaction;
+ loff_t dirty_start = jinode->i_dirty_start;
+ loff_t dirty_end = jinode->i_dirty_end;
+
+ struct writeback_control wbc = {
+ .sync_mode = WB_SYNC_ALL,
+ .nr_to_write = ~0ULL,
+ .range_start = dirty_start,
+ .range_end = dirty_end,
+ };
+
+ return write_cache_pages(mapping, &wbc,
+ ext4_journalled_writepage_callback,
+ transaction);
+}
+
static int ext4_journal_submit_inode_data_buffers(struct jbd2_inode *jinode)
{
- return jbd2_journal_submit_inode_data_buffers(jinode);
+ int ret;
+
+ if (ext4_should_journal_data(jinode->i_vfs_inode))
+ ret = ext4_journalled_submit_inode_data_buffers(jinode);
+ else
+ ret = jbd2_journal_submit_inode_data_buffers(jinode);
+
+ return ret;
}
static int ext4_journal_finish_inode_data_buffers(struct jbd2_inode *jinode)
{
- return jbd2_journal_finish_inode_data_buffers(jinode);
+ int ret = 0;
+
+ if (!ext4_should_journal_data(jinode->i_vfs_inode))
+ ret = jbd2_journal_finish_inode_data_buffers(jinode);
+
+ return ret;
}
static bool system_going_down(void)
--
2.17.1
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