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ext4: data=journal: write-protect pages on j_submit_inode_data_buffers()

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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 the buffers are attached
to the transaction as jbddirty with write_end_fn(), as already done in
__ext4_journalled_writepage().

Signed-off-by: Mauricio Faria de Oliveira <mfo@canonical.com>
Reported-by: Dann Frazier <dann.frazier@canonical.com>
Reported-by: kernel test robot <lkp@intel.com> # wbc.nr_to_write
Suggested-by: Jan Kara <jack@suse.cz>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20201006004841.600488-5-mfo@canonical.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
Mauricio Faria de Oliveira 2020-10-05 21:48:41 -03:00 committed by Theodore Ts'o
parent 64a9f14499
commit afb585a97f
2 changed files with 101 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

25
fs/ext4/inode.c
View File

@ -1911,6 +1911,9 @@ 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;
@ -6062,10 +6065,8 @@ retry_alloc:
size = i_size_read(inode);
/* Page got truncated from under us? */
if (page->mapping != mapping || page_offset(page) > size) {
unlock_page(page);
ret = VM_FAULT_NOPAGE;
ext4_journal_stop(handle);
goto out;
goto out_error;
}
if (page->index == size >> PAGE_SHIFT)
@ -6075,13 +6076,15 @@ retry_alloc:
err = __block_write_begin(page, 0, len, ext4_get_block);
if (!err) {
ret = VM_FAULT_SIGBUS;
if (ext4_walk_page_buffers(handle, page_buffers(page),
0, len, NULL, do_journal_get_write_access)) {
unlock_page(page);
ret = VM_FAULT_SIGBUS;
ext4_journal_stop(handle);
goto out;
}
0, len, NULL, do_journal_get_write_access))
goto out_error;
if (ext4_walk_page_buffers(handle, page_buffers(page),
0, len, NULL, write_end_fn))
goto out_error;
if (ext4_jbd2_inode_add_write(handle, inode, 0, len))
goto out_error;
ext4_set_inode_state(inode, EXT4_STATE_JDATA);
} else {
unlock_page(page);
@ -6096,6 +6099,10 @@ out:
up_read(&EXT4_I(inode)->i_mmap_sem);
sb_end_pagefault(inode->i_sb);
return ret;
out_error:
unlock_page(page);
ext4_journal_stop(handle);
goto out;
}
vm_fault_t ext4_filemap_fault(struct vm_fault *vmf)

87
fs/ext4/super.c
View File

@ -571,6 +571,89 @@ 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 may have to redirty a page (see below.)
*/
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 {
/*
* We have to redirty a page in these cases:
* 1) If buffer is dirty, it means the page was dirty because it
* contains a buffer that needs checkpointing. So the dirty bit
* needs to be preserved so that checkpointing writes the buffer
* properly.
* 2) If buffer is not part of the committing transaction
* (we may have just accidentally come across this buffer because
* inode range tracking is not exact) or if the currently running
* transaction already contains this buffer as well, dirty bit
* needs to be preserved so that the buffer gets writeprotected
* properly on running transaction's commit.
*/
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;
struct writeback_control wbc = {
.sync_mode = WB_SYNC_ALL,
.nr_to_write = LONG_MAX,
.range_start = jinode->i_dirty_start,
.range_end = jinode->i_dirty_end,
};
return write_cache_pages(mapping, &wbc,
ext4_journalled_writepage_callback,
jinode->i_transaction);
}
static int ext4_journal_submit_inode_data_buffers(struct jbd2_inode *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)
{
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)
{
return system_state == SYSTEM_HALT || system_state == SYSTEM_POWER_OFF
@ -4753,9 +4836,9 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
sbi->s_journal->j_commit_callback = ext4_journal_commit_callback;
sbi->s_journal->j_submit_inode_data_buffers =
jbd2_journal_submit_inode_data_buffers;
ext4_journal_submit_inode_data_buffers;
sbi->s_journal->j_finish_inode_data_buffers =
jbd2_journal_finish_inode_data_buffers;
ext4_journal_finish_inode_data_buffers;
no_journal:
if (!test_opt(sb, NO_MBCACHE)) {