block_prepare_write() can dirty freshly created buffer. This is a problem
for data=journal mode because data buffers shouldn't be dirty unless they
are undergoing checkpoint. So we have to tweak get_block function for
data=journal mode to catch the case when block_prepare_write would dirty
the buffer, do the work instead of block_prepare_write, and properly handle
dirty buffer as data=journal mode requires it.
It might be cleaner to avoid using block_prepare_write() for data=journal
mode writes but that would require us to duplicate most of the function
which isn't nice either...
CC: tytso@xxxxxxx
Signed-off-by: Jan Kara <jack@xxxxxxx>
---
fs/ext4/inode.c | 47 +++++++++++++++++++++++++++++++++++++++++++----
1 files changed, 43 insertions(+), 4 deletions(-)
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 81d6054..526404b 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -1388,6 +1388,43 @@ out:
return ret;
}
+static int ext4_journalled_get_block(struct inode *inode, sector_t iblock,
+ struct buffer_head *bh, int create)
+{
+ handle_t *handle = ext4_journal_current_handle();
+ int ret;
+
+ /* This function should ever be used only for real buffers */
+ BUG_ON(!bh->b_page);
+
+ ret = ext4_get_blocks(handle, inode, iblock, 1, bh,
+ create ? EXT4_GET_BLOCKS_CREATE : 0);
+ if (ret > 0) {
+ if (buffer_new(bh)) {
+ struct page *page = bh->b_page;
+
+ /*
+ * This is a terrible hack to avoid block_prepare_write
+ * marking our buffer as dirty
+ */
+ if (PageUptodate(page)) {
+ ret = ext4_journal_get_write_access(handle, bh);
+ if (ret < 0)
+ return ret;
+ unmap_underlying_metadata(bh->b_bdev,
+ bh->b_blocknr);
+ clear_buffer_new(bh);
+ set_buffer_uptodate(bh);
+ ret = jbd2_journal_dirty_metadata(handle, bh);
+ if (ret < 0)
+ return ret;
+ }
+ }
+ ret = 0;
+ }
+ return ret;
+}
+
/*
* `handle' can be NULL if create is zero
*/
@@ -1599,12 +1636,14 @@ retry:
if (ext4_should_dioread_nolock(inode))
ret = block_write_begin(file, mapping, pos, len, flags, pagep,
fsdata, ext4_get_block_write);
- else
+ else if (!ext4_should_journal_data(inode))
ret = block_write_begin(file, mapping, pos, len, flags, pagep,
fsdata, ext4_get_block);
-
- if (!ret && ext4_should_journal_data(inode)) {
- ret = walk_page_buffers(handle, page_buffers(page),
+ else {
+ ret = block_write_begin(file, mapping, pos, len, flags, pagep,
+ fsdata, ext4_journalled_get_block);
+ if (!ret)
+ ret = walk_page_buffers(handle, page_buffers(page),
from, to, NULL, do_journal_get_write_access);
}
--
1.6.4.2
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