[PATCH 5.10 01/22] ext4: check and update i_disksize properly

Greg Kroah-Hartman
2021-10-14T15:01:57Z

From: Zhang Yi <yi.zhang@huawei.com>

[ Upstream commit 4df031ff5876d94b48dd9ee486ba5522382a06b2 ]

After commit 3da40c7b0898 ("ext4: only call ext4_truncate when size <=
isize"), i_disksize could always be updated to i_size in ext4_setattr(),
and we could sure that i_disksize <= i_size since holding inode lock and
if i_disksize < i_size there are delalloc writes pending in the range
upto i_size. If the end of the current write is <= i_size, there's no
need to touch i_disksize since writeback will push i_disksize upto
i_size eventually. So we can switch to check i_size instead of
i_disksize in ext4_da_write_end() when write to the end of the file.
we also could remove ext4_mark_inode_dirty() together because we defer
inode dirtying to generic_write_end() or ext4_da_write_inline_data_end().

Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Link: https://lore.kernel.org/r/20210716122024.1105856-2-yi.zhang@huawei.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/ext4/inode.c | 34 ++++++++++++++++++----------------
1 file changed, 18 insertions(+), 16 deletions(-)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 63a292db7587..f0dcc09e220b 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3090,35 +3090,37 @@ static int ext4_da_write_end(struct file *file,
end = start + copied - 1;

/*
- * generic_write_end() will run mark_inode_dirty() if i_size
- * changes. So let's piggyback the i_disksize mark_inode_dirty
- * into that.
+ * Since we are holding inode lock, we are sure i_disksize <=
+ * i_size. We also know that if i_disksize < i_size, there are
+ * delalloc writes pending in the range upto i_size. If the end of
+ * the current write is <= i_size, there's no need to touch
+ * i_disksize since writeback will push i_disksize upto i_size
+ * eventually. If the end of the current write is > i_size and
+ * inside an allocated block (ext4_da_should_update_i_disksize()
+ * check), we need to update i_disksize here as neither
+ * ext4_writepage() nor certain ext4_writepages() paths not
+ * allocating blocks update i_disksize.
+ *
+ * Note that we defer inode dirtying to generic_write_end() /
+ * ext4_da_write_inline_data_end().
*/
new_i_size = pos + copied;
- if (copied && new_i_size > EXT4_I(inode)->i_disksize) {
+ if (copied && new_i_size > inode->i_size) {
if (ext4_has_inline_data(inode) ||
- ext4_da_should_update_i_disksize(page, end)) {
+ ext4_da_should_update_i_disksize(page, end))
ext4_update_i_disksize(inode, new_i_size);
- /* We need to mark inode dirty even if
- * new_i_size is less that inode->i_size
- * bu greater than i_disksize.(hint delalloc)
- */
- ret = ext4_mark_inode_dirty(handle, inode);
- }
}

if (write_mode != CONVERT_INLINE_DATA &&
ext4_test_inode_state(inode, EXT4_STATE_MAY_INLINE_DATA) &&
ext4_has_inline_data(inode))
- ret2 = ext4_da_write_inline_data_end(inode, pos, len, copied,
+ ret = ext4_da_write_inline_data_end(inode, pos, len, copied,
page);
else
- ret2 = generic_write_end(file, mapping, pos, len, copied,
+ ret = generic_write_end(file, mapping, pos, len, copied,
page, fsdata);

- copied = ret2;
- if (ret2 < 0)
- ret = ret2;
+ copied = ret;
ret2 = ext4_journal_stop(handle);
if (unlikely(ret2 && !ret))
ret = ret2;
--
2.33.0