Unverified Commit 345ca570 authored by openeuler-ci-bot's avatar openeuler-ci-bot Committed by Gitee
Browse files

!14269 iomap: fix zero padding data issue in concurrent append writes 

Merge Pull Request from: @ci-robot 
 
PR sync from: Long Li <leo.lilong@huawei.com>
https://mailweb.openeuler.org/hyperkitty/list/kernel@openeuler.org/message/TN22TZ6X4MA5UIYNZS7JQODNUXZQPFAM/ 
 
https://gitee.com/openeuler/kernel/issues/IB3O3K 
 
Link:https://gitee.com/openeuler/kernel/pulls/14269

 

Reviewed-by: default avatarLi Nan <linan122@huawei.com>
Reviewed-by: default avatarzhangyi (F) <yi.zhang@huawei.com>
Signed-off-by: default avatarLi Nan <linan122@huawei.com>
parents d14e41f4 454ff75b

fs/iomap/buffered-io.c

+47 −0
Original line number Diff line number Diff line
@@ -1409,6 +1409,7 @@ iomap_add_to_ioend(struct inode *inode, loff_t offset, struct page *page, 
	unsigned len = i_blocksize(inode);

	unsigned poff = offset & (PAGE_SIZE - 1);

	bool merged, same_page = false;

	loff_t isize = i_size_read(inode);



	if (!wpc->ioend || !iomap_can_add_to_ioend(wpc, offset, sector)) {

		if (wpc->ioend)
@@ -1429,7 +1430,53 @@ iomap_add_to_ioend(struct inode *inode, loff_t offset, struct page *page, 
		bio_add_page(wpc->ioend->io_bio, page, len, poff);

	}



	/*

	 * Clamp io_offset and io_size to the incore EOF so that ondisk

	 * file size updates in the ioend completion are byte-accurate.

	 * This avoids recovering files with zeroed tail regions when

	 * writeback races with appending writes:

	 *

	 *    Thread 1:                  Thread 2:

	 *    ------------               -----------

	 *    write [A, A+B]

	 *    update inode size to A+B

	 *    submit I/O [A, A+BS]

	 *                               write [A+B, A+B+C]

	 *                               update inode size to A+B+C

	 *    <I/O completes, updates disk size to min(A+B+C, A+BS)>

	 *    <power failure>

	 *

	 *  After reboot:

	 *    1) with A+B+C < A+BS, the file has zero padding in range

	 *       [A+B, A+B+C]

	 *

	 *    |<     Block Size (BS)   >|

	 *    |DDDDDDDDDDDD0000000000000|

	 *    ^           ^        ^

	 *    A          A+B     A+B+C

	 *                       (EOF)

	 *

	 *    2) with A+B+C > A+BS, the file has zero padding in range

	 *       [A+B, A+BS]

	 *

	 *    |<     Block Size (BS)   >|<     Block Size (BS)    >|

	 *    |DDDDDDDDDDDD0000000000000|00000000000000000000000000|

	 *    ^           ^             ^           ^

	 *    A          A+B           A+BS       A+B+C

	 *                             (EOF)

	 *

	 *    D = Valid Data

	 *    0 = Zero Padding

	 *

	 * Note that this defeats the ability to chain the ioends of

	 * appending writes. Writeback beyond EOF block may occur in

	 * concurrent scenarios(e.g. racing with truncate) and io_size

	 * should not be trimmed in such cases.

	 */

	wpc->ioend->io_size += len;

	if (offset < isize && offset + len > isize)

		wpc->ioend->io_size = isize - wpc->ioend->io_offset;



	wbc_account_cgroup_owner(wbc, page, len);

}

include/linux/iomap.h

+1 −1
Original line number Diff line number Diff line
@@ -229,7 +229,7 @@ struct iomap_ioend { 
	u16			io_flags;	/* IOMAP_F_* */

	u32			io_folios;	/* folios added to ioend */

	struct inode		*io_inode;	/* file being written to */

	size_t			io_size;	/* size of the extent */

	size_t			io_size;	/* size of data within eof */

	loff_t			io_offset;	/* offset in the file */

	void			*io_private;	/* file system private data */

	sector_t		io_sector;	/* start sector of ioend */