On Thu, Oct 17, 2019 at 07:56:11PM +0200, Christoph Hellwig wrote: > From: Dave Chinner <dchinner@xxxxxxxxxx> > > When doing a direct IO that spans the current EOF, and there are > written blocks beyond EOF that extend beyond the current write, the > only metadata update that needs to be done is a file size extension. > > However, we don't mark such iomaps as IOMAP_F_DIRTY to indicate that > there is IO completion metadata updates required, and hence we may > fail to correctly sync file size extensions made in IO completion > when O_DSYNC writes are being used and the hardware supports FUA. > > Hence when setting IOMAP_F_DIRTY, we need to also take into account > whether the iomap spans the current EOF. If it does, then we need to > mark it dirty so that IO completion will call generic_write_sync() > to flush the inode size update to stable storage correctly. > > Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx> > Signed-off-by: Christoph Hellwig <hch@xxxxxx> Looks ok, but need fixes tag. Also, might it be wise to split off the ext4 section into a separate patch so that it can be backported separately? Reviewed-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx> --D > --- > fs/ext4/inode.c | 9 ++++++++- > fs/xfs/xfs_iomap.c | 7 +++++++ > include/linux/iomap.h | 2 ++ > 3 files changed, 17 insertions(+), 1 deletion(-) > > diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c > index 516faa280ced..e9dc52537e5b 100644 > --- a/fs/ext4/inode.c > +++ b/fs/ext4/inode.c > @@ -3523,9 +3523,16 @@ static int ext4_iomap_begin(struct inode *inode, loff_t offset, loff_t length, > return ret; > } > > + /* > + * Writes that span EOF might trigger an IO size update on completion, > + * so consider them to be dirty for the purposes of O_DSYNC even if > + * there is no other metadata changes being made or are pending here. > + */ > iomap->flags = 0; > - if (ext4_inode_datasync_dirty(inode)) > + if (ext4_inode_datasync_dirty(inode) || > + offset + length > i_size_read(inode)) > iomap->flags |= IOMAP_F_DIRTY; > + > iomap->bdev = inode->i_sb->s_bdev; > iomap->dax_dev = sbi->s_daxdev; > iomap->offset = (u64)first_block << blkbits; > diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c > index f780e223b118..32993c2acbd9 100644 > --- a/fs/xfs/xfs_iomap.c > +++ b/fs/xfs/xfs_iomap.c > @@ -1049,6 +1049,13 @@ xfs_file_iomap_begin( > trace_xfs_iomap_alloc(ip, offset, length, XFS_DATA_FORK, &imap); > > out_finish: > + /* > + * Writes that span EOF might trigger an IO size update on completion, > + * so consider them to be dirty for the purposes of O_DSYNC even if > + * there is no other metadata changes pending or have been made here. > + */ > + if ((flags & IOMAP_WRITE) && offset + length > i_size_read(inode)) > + iomap->flags |= IOMAP_F_DIRTY; > return xfs_bmbt_to_iomap(ip, iomap, &imap, shared); > > out_found: > diff --git a/include/linux/iomap.h b/include/linux/iomap.h > index 7aa5d6117936..24bd227d59f9 100644 > --- a/include/linux/iomap.h > +++ b/include/linux/iomap.h > @@ -32,6 +32,8 @@ struct vm_fault; > * > * IOMAP_F_DIRTY indicates the inode has uncommitted metadata needed to access > * written data and requires fdatasync to commit them to persistent storage. > + * This needs to take into account metadata changes that *may* be made at IO > + * completion, such as file size updates from direct IO. > */ > #define IOMAP_F_NEW 0x01 /* blocks have been newly allocated */ > #define IOMAP_F_DIRTY 0x02 /* uncommitted metadata */ > -- > 2.20.1 >
