Commit 7d81ec02 authored by Zhang Yi's avatar Zhang Yi Committed by Theodore Ts'o
Browse files

ext4: ensure zeroed partial blocks are persisted in SYNC mode 



In ext4_zero_range() and ext4_punch_hole(), when operating in SYNC mode
and zeroing a partial block, only data=journal modes guarantee that the
zeroed data is synchronously persisted after the operation completes.
For data=ordered/writeback mode and non-journal modes, this guarantee is
missing.

Introduce a partial_zero parameter to explicitly trigger writeback for
all scenarios where a partial block is zeroed, ensuring the zeroed data
is durably persisted.

Signed-off-by: default avatarZhang Yi <yi.zhang@huawei.com>
Link: https://patch.msgid.link/20260327102939.1095257-10-yi.zhang@huaweicloud.com


Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
parent c4602a1d

fs/ext4/ext4.h

+1 −1
Original line number Diff line number Diff line
@@ -3099,7 +3099,7 @@ extern int ext4_meta_trans_blocks(struct inode *inode, int lblocks, 
				  int pextents);

extern int ext4_block_zero_eof(struct inode *inode, loff_t from, loff_t end);

extern int ext4_zero_partial_blocks(struct inode *inode, loff_t lstart,

				    loff_t length);

				    loff_t length, bool *did_zero);

extern vm_fault_t ext4_page_mkwrite(struct vm_fault *vmf);

extern qsize_t *ext4_get_reserved_space(struct inode *inode);

extern int ext4_get_projid(struct inode *inode, kprojid_t *projid);

fs/ext4/extents.c

+8 −1
Original line number Diff line number Diff line
@@ -4702,6 +4702,7 @@ static long ext4_zero_range(struct file *file, loff_t offset, 
	loff_t align_start, align_end, new_size = 0;

	loff_t end = offset + len;

	unsigned int blocksize = i_blocksize(inode);

	bool partial_zeroed = false;

	int ret, flags;



	trace_ext4_zero_range(inode, offset, len, mode);
@@ -4757,9 +4758,15 @@ static long ext4_zero_range(struct file *file, loff_t offset, 
		return ret;



	/* Zero out partial block at the edges of the range */

	ret = ext4_zero_partial_blocks(inode, offset, len);

	ret = ext4_zero_partial_blocks(inode, offset, len, &partial_zeroed);

	if (ret)

		return ret;

	if (((file->f_flags & O_SYNC) || IS_SYNC(inode)) && partial_zeroed) {

		ret = filemap_write_and_wait_range(inode->i_mapping, offset,

						   end - 1);

		if (ret)

			return ret;

	}



	handle = ext4_journal_start(inode, EXT4_HT_MISC, 1);

	if (IS_ERR(handle)) {

fs/ext4/inode.c

+14 −5
Original line number Diff line number Diff line
@@ -4257,7 +4257,8 @@ int ext4_block_zero_eof(struct inode *inode, loff_t from, loff_t end) 
	return 0;

}



int ext4_zero_partial_blocks(struct inode *inode, loff_t lstart, loff_t length)

int ext4_zero_partial_blocks(struct inode *inode, loff_t lstart, loff_t length,

			     bool *did_zero)

{

	struct super_block *sb = inode->i_sb;

	unsigned partial_start, partial_end;
@@ -4274,20 +4275,21 @@ int ext4_zero_partial_blocks(struct inode *inode, loff_t lstart, loff_t length) 
	/* Handle partial zero within the single block */

	if (start == end &&

	    (partial_start || (partial_end != sb->s_blocksize - 1))) {

		err = ext4_block_zero_range(inode, lstart, length, NULL, NULL);

		err = ext4_block_zero_range(inode, lstart, length, did_zero,

					    NULL);

		return err;

	}

	/* Handle partial zero out on the start of the range */

	if (partial_start) {

		err = ext4_block_zero_range(inode, lstart, sb->s_blocksize,

					    NULL, NULL);

					    did_zero, NULL);

		if (err)

			return err;

	}

	/* Handle partial zero out on the end of the range */

	if (partial_end != sb->s_blocksize - 1)

		err = ext4_block_zero_range(inode, byte_end - partial_end,

					    partial_end + 1, NULL, NULL);

					    partial_end + 1, did_zero, NULL);

	return err;

}
@@ -4436,6 +4438,7 @@ int ext4_punch_hole(struct file *file, loff_t offset, loff_t length) 
	loff_t end = offset + length;

	handle_t *handle;

	unsigned int credits;

	bool partial_zeroed = false;

	int ret;



	trace_ext4_punch_hole(inode, offset, length, 0);
@@ -4471,9 +4474,15 @@ int ext4_punch_hole(struct file *file, loff_t offset, loff_t length) 
	if (ret)

		return ret;



	ret = ext4_zero_partial_blocks(inode, offset, length);

	ret = ext4_zero_partial_blocks(inode, offset, length, &partial_zeroed);

	if (ret)

		return ret;

	if (((file->f_flags & O_SYNC) || IS_SYNC(inode)) && partial_zeroed) {

		ret = filemap_write_and_wait_range(inode->i_mapping, offset,

						   end - 1);

		if (ret)

			return ret;

	}



	if (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))

		credits = ext4_chunk_trans_extent(inode, 0);