[PATCH 3/3] iomap: fall back to buffered writes for invalidation failures

Christoph Hellwig
2020-07-21T18:32:16Z

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>
Acked-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
---
fs/ext4/file.c | 2 ++
fs/gfs2/file.c | 3 ++-
fs/iomap/direct-io.c | 16 +++++++++++-----
fs/iomap/trace.h | 1 +
fs/xfs/xfs_file.c | 4 ++--
fs/zonefs/super.c | 7 +++++--
6 files changed, 23 insertions(+), 10 deletions(-)

diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index 2a01e31a032c4c..129cc1dd6b7952 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 == -ENOTBLK)
+ 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 bebde537ac8cf2..b085a3bea4f0fd 100644
--- a/fs/gfs2/file.c
+++ b/fs/gfs2/file.c
@@ -835,7 +835,8 @@ 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 == -ENOTBLK)
+ 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..c1aafb2ab99072 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"

@@ -401,6 +402,9 @@ iomap_dio_actor(struct inode *inode, loff_t pos, loff_t length,
* can be mapped into multiple disjoint IOs and only a subset of the IOs issued
* may be pure data writes. In that case, we still need to do a full data sync
* completion.
+ *
+ * Returns -ENOTBLK In case of a page invalidation invalidation failure for
+ * writes. The callers needs to fall back to buffered I/O in this case.
*/
ssize_t
iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
@@ -478,13 +482,15 @@ 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 = -ENOTBLK;
+ 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 a6ef90457abf97..1b4517fc55f1b9 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 fallback to buffered IO after short writes for XFS, direct I/O
+ * will either complete fully or return an error.
*/
ASSERT(ret < 0 || ret == count);
return ret;
diff --git a/fs/zonefs/super.c b/fs/zonefs/super.c
index 07bc42d62673ce..d0a04528a7e18e 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) {
+ ssize_t ret = zonefs_file_dio_write(iocb, from);
+ if (ret != -ENOTBLK)
+ return ret;
+ }

return zonefs_file_buffered_write(iocb, from);
}
--
2.27.0