From: Darrick J. Wong <darrick.wong@oracle.com>
To: cluster-devel.redhat.com
Subject: [Cluster-devel] [PATCH 2/2] iomap: fall back to buffered writes for invalidation failures
Date: Mon, 13 Jul 2020 08:39:20 -0700 [thread overview]
Message-ID: <20200713153920.GU7606@magnolia> (raw)
In-Reply-To: <20200713074633.875946-3-hch@lst.de>
On Mon, Jul 13, 2020 at 09:46:33AM +0200, Christoph Hellwig wrote:
> Failing to invalid the page cache means data in incoherent, which is
> a very bad state for the system. Always fall back to buffered I/O
> through the page cache if we can't invalidate mappings.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
> fs/ext4/file.c | 2 ++
> fs/gfs2/file.c | 3 ++-
> fs/iomap/direct-io.c | 13 ++++++++-----
> fs/iomap/trace.h | 1 +
> fs/xfs/xfs_file.c | 4 ++--
> fs/zonefs/super.c | 7 +++++--
> 6 files changed, 20 insertions(+), 10 deletions(-)
>
> diff --git a/fs/ext4/file.c b/fs/ext4/file.c
> index 2a01e31a032c4c..0da6c2a2c32c1e 100644
> --- a/fs/ext4/file.c
> +++ b/fs/ext4/file.c
> @@ -544,6 +544,8 @@ static ssize_t ext4_dio_write_iter(struct kiocb *iocb, struct iov_iter *from)
> iomap_ops = &ext4_iomap_overwrite_ops;
> ret = iomap_dio_rw(iocb, from, iomap_ops, &ext4_dio_write_ops,
> is_sync_kiocb(iocb) || unaligned_io || extend);
> + if (ret == -EREMCHG)
> + ret = 0;
>
> if (extend)
> ret = ext4_handle_inode_extension(inode, offset, ret, count);
> diff --git a/fs/gfs2/file.c b/fs/gfs2/file.c
> index fe305e4bfd3734..c7907d40c61d17 100644
> --- a/fs/gfs2/file.c
> +++ b/fs/gfs2/file.c
> @@ -814,7 +814,8 @@ static ssize_t gfs2_file_direct_write(struct kiocb *iocb, struct iov_iter *from)
>
> ret = iomap_dio_rw(iocb, from, &gfs2_iomap_ops, NULL,
> is_sync_kiocb(iocb));
> -
> + if (ret == -EREMCHG)
> + ret = 0;
> out:
> gfs2_glock_dq(&gh);
> out_uninit:
> diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
> index 190967e87b69e4..62626235cdbe8d 100644
> --- a/fs/iomap/direct-io.c
> +++ b/fs/iomap/direct-io.c
> @@ -10,6 +10,7 @@
> #include <linux/backing-dev.h>
> #include <linux/uio.h>
> #include <linux/task_io_accounting_ops.h>
> +#include "trace.h"
>
> #include "../internal.h"
>
> @@ -478,13 +479,15 @@ iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
> if (iov_iter_rw(iter) == WRITE) {
> /*
> * Try to invalidate cache pages for the range we are writing.
> - * If this invalidation fails, tough, the write will still work,
> - * but racing two incompatible write paths is a pretty crazy
> - * thing to do, so we don't support it 100%.
> + * If this invalidation fails, let the caller fall back to
> + * buffered I/O.
> */
> if (invalidate_inode_pages2_range(mapping, pos >> PAGE_SHIFT,
> - end >> PAGE_SHIFT))
> - dio_warn_stale_pagecache(iocb->ki_filp);
> + end >> PAGE_SHIFT)) {
> + trace_iomap_dio_invalidate_fail(inode, pos, count);
> + ret = -EREMCHG;
-ENOTBLK is already being used as a "magic" return code that means
"retry this direct write as a buffered write". Shouldn't we use that
instead?
-EREMCHG was a private hack we put in XFS for the one case where a
direct write had to be done through the page cache (non block-aligned
COW), but maybe it's time we put that to rest since the rest of the
world apparently thinks the magic fallback code is -ENOTBLK.
--D
> + goto out_free_dio;
> + }
>
> if (!wait_for_completion && !inode->i_sb->s_dio_done_wq) {
> ret = sb_init_dio_done_wq(inode->i_sb);
> diff --git a/fs/iomap/trace.h b/fs/iomap/trace.h
> index 5693a39d52fb63..fdc7ae388476f5 100644
> --- a/fs/iomap/trace.h
> +++ b/fs/iomap/trace.h
> @@ -74,6 +74,7 @@ DEFINE_EVENT(iomap_range_class, name, \
> DEFINE_RANGE_EVENT(iomap_writepage);
> DEFINE_RANGE_EVENT(iomap_releasepage);
> DEFINE_RANGE_EVENT(iomap_invalidatepage);
> +DEFINE_RANGE_EVENT(iomap_dio_invalidate_fail);
>
> #define IOMAP_TYPE_STRINGS \
> { IOMAP_HOLE, "HOLE" }, \
> diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
> index 00db81eac80d6c..551cca39fa3ba6 100644
> --- a/fs/xfs/xfs_file.c
> +++ b/fs/xfs/xfs_file.c
> @@ -553,8 +553,8 @@ xfs_file_dio_aio_write(
> xfs_iunlock(ip, iolock);
>
> /*
> - * No fallback to buffered IO on errors for XFS, direct IO will either
> - * complete fully or fail.
> + * No partial fallback to buffered IO on errors for XFS, direct IO will
> + * either complete fully or fail.
> */
> ASSERT(ret < 0 || ret == count);
> return ret;
> diff --git a/fs/zonefs/super.c b/fs/zonefs/super.c
> index 07bc42d62673ce..793850454b752f 100644
> --- a/fs/zonefs/super.c
> +++ b/fs/zonefs/super.c
> @@ -786,8 +786,11 @@ static ssize_t zonefs_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
> if (iocb->ki_pos >= ZONEFS_I(inode)->i_max_size)
> return -EFBIG;
>
> - if (iocb->ki_flags & IOCB_DIRECT)
> - return zonefs_file_dio_write(iocb, from);
> + if (iocb->ki_flags & IOCB_DIRECT) {
> + ret = zonefs_file_dio_write(iocb, from);
> + if (ret != -EREMCHG)
> + return ret;
> + }
>
> return zonefs_file_buffered_write(iocb, from);
> }
> --
> 2.26.2
>
next prev parent reply other threads:[~2020-07-13 15:39 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-13 7:46 [Cluster-devel] RFC: iomap write invalidation Christoph Hellwig
2020-07-13 7:46 ` [Cluster-devel] [PATCH 1/2] iomap: Only invalidate page cache pages on direct IO writes Christoph Hellwig
2020-07-13 7:46 ` [Cluster-devel] [PATCH 2/2] iomap: fall back to buffered writes for invalidation failures Christoph Hellwig
2020-07-13 11:55 ` Matthew Wilcox
2020-07-14 11:00 ` Christoph Hellwig
2020-07-13 12:20 ` Goldwyn Rodrigues
2020-07-13 16:09 ` David Sterba
2020-07-13 15:39 ` Darrick J. Wong [this message]
2020-07-14 11:00 ` Christoph Hellwig
2020-07-14 1:41 ` Damien Le Moal
2020-07-15 1:47 ` [Cluster-devel] RFC: iomap write invalidation Dave Chinner
2020-07-20 21:51 ` Goldwyn Rodrigues
2020-07-21 14:53 ` Christoph Hellwig
2020-07-21 14:59 ` Darrick J. Wong
2020-07-21 15:04 ` Matthew Wilcox
2020-07-21 15:06 ` Christoph Hellwig
2020-07-21 15:14 ` Matthew Wilcox
2020-07-21 15:16 ` Christoph Hellwig
2020-07-21 15:27 ` Darrick J. Wong
2020-07-21 15:41 ` Christoph Hellwig
2020-07-21 15:59 ` Darrick J. Wong
2020-07-21 16:01 ` Christoph Hellwig
2020-07-21 16:05 ` Darrick J. Wong
2020-07-21 15:31 ` Matthew Wilcox
2020-07-21 15:42 ` Christoph Hellwig
2020-07-21 15:52 ` Matthew Wilcox
2020-07-21 16:03 ` Darrick J. Wong
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