Re: [PATCH 04/12] xfs: initialize ioma->flags in xfs_bmbt_to_iomap

Darrick J. Wong
2019-06-24T14:57:37Z

On Mon, Jun 24, 2019 at 07:52:45AM +0200, Christoph Hellwig wrote:
> Currently we don't overwrite the flags field in the iomap in
> xfs_bmbt_to_iomap. This works fine with 0-initialized iomaps on stack,
> but is harmful once we want to be able to reuse an iomap in the
> writeback code.

Is that going to affect all the other iomap users, or is xfs the only
one that assumes zero-initialized iomaps being passed into
->iomap_begin?

--D

> Replace the shared paramter with a set of initial
> flags an thus ensures the flags field is always reinitialized.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
> fs/xfs/xfs_iomap.c | 28 +++++++++++++++++-----------
> fs/xfs/xfs_iomap.h | 2 +-
> fs/xfs/xfs_pnfs.c | 2 +-
> 3 files changed, 19 insertions(+), 13 deletions(-)
>
> diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
> index 63d323916bba..6b29452bfba0 100644
> --- a/fs/xfs/xfs_iomap.c
> +++ b/fs/xfs/xfs_iomap.c
> @@ -57,7 +57,7 @@ xfs_bmbt_to_iomap(
> struct xfs_inode *ip,
> struct iomap *iomap,
> struct xfs_bmbt_irec *imap,
> - bool shared)
> + u16 flags)
> {
> struct xfs_mount *mp = ip->i_mount;
>
> @@ -82,12 +82,11 @@ xfs_bmbt_to_iomap(
> iomap->length = XFS_FSB_TO_B(mp, imap->br_blockcount);
> iomap->bdev = xfs_find_bdev_for_inode(VFS_I(ip));
> iomap->dax_dev = xfs_find_daxdev_for_inode(VFS_I(ip));
> + iomap->flags = flags;
>
> if (xfs_ipincount(ip) &&
> (ip->i_itemp->ili_fsync_fields & ~XFS_ILOG_TIMESTAMP))
> iomap->flags |= IOMAP_F_DIRTY;
> - if (shared)
> - iomap->flags |= IOMAP_F_SHARED;
> return 0;
> }
>
> @@ -543,6 +542,7 @@ xfs_file_iomap_begin_delay(
> struct xfs_iext_cursor icur, ccur;
> xfs_fsblock_t prealloc_blocks = 0;
> bool eof = false, cow_eof = false, shared = false;
> + u16 iomap_flags = 0;
> int whichfork = XFS_DATA_FORK;
> int error = 0;
>
> @@ -710,7 +710,7 @@ xfs_file_iomap_begin_delay(
> * Flag newly allocated delalloc blocks with IOMAP_F_NEW so we punch
> * them out if the write happens to fail.
> */
> - iomap->flags |= IOMAP_F_NEW;
> + iomap_flags |= IOMAP_F_NEW;
> trace_xfs_iomap_alloc(ip, offset, count, whichfork,
> whichfork == XFS_DATA_FORK ? &imap : &cmap);
> done:
> @@ -718,14 +718,17 @@ xfs_file_iomap_begin_delay(
> if (imap.br_startoff > offset_fsb) {
> xfs_trim_extent(&cmap, offset_fsb,
> imap.br_startoff - offset_fsb);
> - error = xfs_bmbt_to_iomap(ip, iomap, &cmap, true);
> + error = xfs_bmbt_to_iomap(ip, iomap, &cmap,
> + IOMAP_F_SHARED);
> goto out_unlock;
> }
> /* ensure we only report blocks we have a reservation for */
> xfs_trim_extent(&imap, cmap.br_startoff, cmap.br_blockcount);
> shared = true;
> }
> - error = xfs_bmbt_to_iomap(ip, iomap, &imap, shared);
> + if (shared)
> + iomap_flags |= IOMAP_F_SHARED;
> + error = xfs_bmbt_to_iomap(ip, iomap, &imap, iomap_flags);
> out_unlock:
> xfs_iunlock(ip, XFS_ILOCK_EXCL);
> return error;
> @@ -933,6 +936,7 @@ xfs_file_iomap_begin(
> xfs_fileoff_t offset_fsb, end_fsb;
> int nimaps = 1, error = 0;
> bool shared = false;
> + u16 iomap_flags = 0;
> unsigned lockmode;
>
> if (XFS_FORCED_SHUTDOWN(mp))
> @@ -1048,11 +1052,13 @@ xfs_file_iomap_begin(
> if (error)
> return error;
>
> - iomap->flags |= IOMAP_F_NEW;
> + iomap_flags |= IOMAP_F_NEW;
> trace_xfs_iomap_alloc(ip, offset, length, XFS_DATA_FORK, &imap);
>
> out_finish:
> - return xfs_bmbt_to_iomap(ip, iomap, &imap, shared);
> + if (shared)
> + iomap_flags |= IOMAP_F_SHARED;
> + return xfs_bmbt_to_iomap(ip, iomap, &imap, iomap_flags);
>
> out_found:
> ASSERT(nimaps);
> @@ -1196,7 +1202,7 @@ xfs_seek_iomap_begin(
> if (data_fsb < cow_fsb + cmap.br_blockcount)
> end_fsb = min(end_fsb, data_fsb);
> xfs_trim_extent(&cmap, offset_fsb, end_fsb);
> - error = xfs_bmbt_to_iomap(ip, iomap, &cmap, true);
> + error = xfs_bmbt_to_iomap(ip, iomap, &cmap, IOMAP_F_SHARED);
> /*
> * This is a COW extent, so we must probe the page cache
> * because there could be dirty page cache being backed
> @@ -1218,7 +1224,7 @@ xfs_seek_iomap_begin(
> imap.br_state = XFS_EXT_NORM;
> done:
> xfs_trim_extent(&imap, offset_fsb, end_fsb);
> - error = xfs_bmbt_to_iomap(ip, iomap, &imap, false);
> + error = xfs_bmbt_to_iomap(ip, iomap, &imap, 0);
> out_unlock:
> xfs_iunlock(ip, lockmode);
> return error;
> @@ -1264,7 +1270,7 @@ xfs_xattr_iomap_begin(
> if (error)
> return error;
> ASSERT(nimaps);
> - return xfs_bmbt_to_iomap(ip, iomap, &imap, false);
> + return xfs_bmbt_to_iomap(ip, iomap, &imap, 0);
> }
>
> const struct iomap_ops xfs_xattr_iomap_ops = {
> diff --git a/fs/xfs/xfs_iomap.h b/fs/xfs/xfs_iomap.h
> index 5c2f6aa6d78f..71d0ae460c44 100644
> --- a/fs/xfs/xfs_iomap.h
> +++ b/fs/xfs/xfs_iomap.h
> @@ -16,7 +16,7 @@ int xfs_iomap_write_direct(struct xfs_inode *, xfs_off_t, size_t,
> int xfs_iomap_write_unwritten(struct xfs_inode *, xfs_off_t, xfs_off_t, bool);
>
> int xfs_bmbt_to_iomap(struct xfs_inode *, struct iomap *,
> - struct xfs_bmbt_irec *, bool shared);
> + struct xfs_bmbt_irec *, u16);
> xfs_extlen_t xfs_eof_alignment(struct xfs_inode *ip, xfs_extlen_t extsize);
>
> static inline xfs_filblks_t
> diff --git a/fs/xfs/xfs_pnfs.c b/fs/xfs/xfs_pnfs.c
> index bde2c9f56a46..12f664785248 100644
> --- a/fs/xfs/xfs_pnfs.c
> +++ b/fs/xfs/xfs_pnfs.c
> @@ -185,7 +185,7 @@ xfs_fs_map_blocks(
> }
> xfs_iunlock(ip, XFS_IOLOCK_EXCL);
>
> - error = xfs_bmbt_to_iomap(ip, iomap, &imap, false);
> + error = xfs_bmbt_to_iomap(ip, iomap, &imap, 0);
> *device_generation = mp->m_generation;
> return error;
> out_unlock:
> --
> 2.20.1
>