On Tue, Nov 05, 2019 at 11:01:51PM +1100, Matthew Bobrowski wrote:
> In preparation for implementing the iomap direct I/O modifications,
> the inode extension/truncate code needs to be moved out from the
> ext4_iomap_end() callback. For direct I/O, if the current code
> remained, it would behave incorrrectly. Updating the inode size prior
> to converting unwritten extents would potentially allow a racing
> direct I/O read to find unwritten extents before being converted
> correctly.
>
> The inode extension/truncate code now resides within a new helper
> ext4_handle_inode_extension(). This function has been designed so that
> it can accommodate for both DAX and direct I/O extension/truncate
> operations.
>
> Signed-off-by: Matthew Bobrowski <mbobrowski@xxxxxxxxxxxxxx>
> Reviewed-by: Jan Kara <jack@xxxxxxx>
> Reviewed-by: Ritesh Harjani <riteshh@xxxxxxxxxxxxx>
> ---
> fs/ext4/file.c | 89 ++++++++++++++++++++++++++++++++++++++++++++++++-
> fs/ext4/inode.c | 48 +-------------------------
> 2 files changed, 89 insertions(+), 48 deletions(-)
>
> diff --git a/fs/ext4/file.c b/fs/ext4/file.c
> index 440f4c6ba4ee..ec54fec96a81 100644
> --- a/fs/ext4/file.c
> +++ b/fs/ext4/file.c
> @@ -33,6 +33,7 @@
> #include "ext4_jbd2.h"
> #include "xattr.h"
> #include "acl.h"
> +#include "truncate.h"
>
> static bool ext4_dio_supported(struct inode *inode)
> {
> @@ -234,12 +235,95 @@ static ssize_t ext4_write_checks(struct kiocb *iocb, struct iov_iter *from)
> return iov_iter_count(from);
> }
>
> +static ssize_t ext4_handle_inode_extension(struct inode *inode, loff_t offset,
> + ssize_t written, size_t count)
> +{
> + handle_t *handle;
> + bool truncate = false;
> + u8 blkbits = inode->i_blkbits;
> + ext4_lblk_t written_blk, end_blk;
> +
> + /*
> + * Note that EXT4_I(inode)->i_disksize can get extended up to
> + * inode->i_size while the I/O was running due to writeback of delalloc
> + * blocks. But, the code in ext4_iomap_alloc() is careful to use
> + * zeroed/unwritten extents if this is possible; thus we won't leave
> + * uninitialized blocks in a file even if we didn't succeed in writing
> + * as much as we intended.
> + */
> + WARN_ON_ONCE(i_size_read(inode) < EXT4_I(inode)->i_disksize);
> + if (offset + count <= EXT4_I(inode)->i_disksize) {
> + /*
> + * We need to ensure that the inode is removed from the orphan
> + * list if it has been added prematurely, due to writeback of
> + * delalloc blocks.
> + */
> + if (!list_empty(&EXT4_I(inode)->i_orphan) && inode->i_nlink) {
> + handle = ext4_journal_start(inode, EXT4_HT_INODE, 2);
> +
> + if (IS_ERR(handle)) {
> + ext4_orphan_del(NULL, inode);
> + return PTR_ERR(handle);
> + }
> +
> + ext4_orphan_del(handle, inode);
> + ext4_journal_stop(handle);
I keep seeing this chunk (and the ext4_orphan_add chunk) bouncing around
through this patchset, which causes me to wonder -- would it be useful
to refactor these into small helpers? Or is it really just the same two
orphan_add/del chunks bouncing around multiple places?
--D
> + }
> +
> + return written;
> + }
> +
> + if (written < 0)
> + goto truncate;
> +
> + handle = ext4_journal_start(inode, EXT4_HT_INODE, 2);
> + if (IS_ERR(handle)) {
> + written = PTR_ERR(handle);
> + goto truncate;
> + }
> +
> + if (ext4_update_inode_size(inode, offset + written))
> + ext4_mark_inode_dirty(handle, inode);
> +
> + /*
> + * We may need to truncate allocated but not written blocks beyond EOF.
> + */
> + written_blk = ALIGN(offset + written, 1 << blkbits);
> + end_blk = ALIGN(offset + count, 1 << blkbits);
> + if (written_blk < end_blk && ext4_can_truncate(inode))
> + truncate = true;
> +
> + /*
> + * Remove the inode from the orphan list if it has been extended and
> + * everything went OK.
> + */
> + if (!truncate && inode->i_nlink)
> + ext4_orphan_del(handle, inode);
> + ext4_journal_stop(handle);
> +
> + if (truncate) {
> +truncate:
> + ext4_truncate_failed_write(inode);
> + /*
> + * If the truncate operation failed early, then the inode may
> + * still be on the orphan list. In that case, we need to try
> + * remove the inode from the in-memory linked list.
> + */
> + if (inode->i_nlink)
> + ext4_orphan_del(NULL, inode);
> + }
> +
> + return written;
> +}
> +
> #ifdef CONFIG_FS_DAX
> static ssize_t
> ext4_dax_write_iter(struct kiocb *iocb, struct iov_iter *from)
> {
> - struct inode *inode = file_inode(iocb->ki_filp);
> ssize_t ret;
> + size_t count;
> + loff_t offset;
> + struct inode *inode = file_inode(iocb->ki_filp);
>
> if (!inode_trylock(inode)) {
> if (iocb->ki_flags & IOCB_NOWAIT)
> @@ -256,7 +340,10 @@ ext4_dax_write_iter(struct kiocb *iocb, struct iov_iter *from)
> if (ret)
> goto out;
>
> + offset = iocb->ki_pos;
> + count = iov_iter_count(from);
> ret = dax_iomap_rw(iocb, from, &ext4_iomap_ops);
> + ret = ext4_handle_inode_extension(inode, offset, ret, count);
> out:
> inode_unlock(inode);
> if (ret > 0)
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 9bd80df6b856..071a1f976aab 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -3583,53 +3583,7 @@ static int ext4_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
> static int ext4_iomap_end(struct inode *inode, loff_t offset, loff_t length,
> ssize_t written, unsigned flags, struct iomap *iomap)
> {
> - int ret = 0;
> - handle_t *handle;
> - int blkbits = inode->i_blkbits;
> - bool truncate = false;
> -
> - if (!(flags & IOMAP_WRITE) || (flags & IOMAP_FAULT))
> - return 0;
> -
> - handle = ext4_journal_start(inode, EXT4_HT_INODE, 2);
> - if (IS_ERR(handle)) {
> - ret = PTR_ERR(handle);
> - goto orphan_del;
> - }
> - if (ext4_update_inode_size(inode, offset + written))
> - ext4_mark_inode_dirty(handle, inode);
> - /*
> - * We may need to truncate allocated but not written blocks beyond EOF.
> - */
> - if (iomap->offset + iomap->length >
> - ALIGN(inode->i_size, 1 << blkbits)) {
> - ext4_lblk_t written_blk, end_blk;
> -
> - written_blk = (offset + written) >> blkbits;
> - end_blk = (offset + length) >> blkbits;
> - if (written_blk < end_blk && ext4_can_truncate(inode))
> - truncate = true;
> - }
> - /*
> - * Remove inode from orphan list if we were extending a inode and
> - * everything went fine.
> - */
> - if (!truncate && inode->i_nlink &&
> - !list_empty(&EXT4_I(inode)->i_orphan))
> - ext4_orphan_del(handle, inode);
> - ext4_journal_stop(handle);
> - if (truncate) {
> - ext4_truncate_failed_write(inode);
> -orphan_del:
> - /*
> - * If truncate failed early the inode might still be on the
> - * orphan list; we need to make sure the inode is removed from
> - * the orphan list in that case.
> - */
> - if (inode->i_nlink)
> - ext4_orphan_del(NULL, inode);
> - }
> - return ret;
> + return 0;
> }
>
> const struct iomap_ops ext4_iomap_ops = {
> --
> 2.20.1
>
