On 2020/07/13 16:51, Christoph Hellwig wrote: > Failing to invalid the page cache means data in incoherent, which is
s/in incoherent/is incoherent > 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 <h...@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; I am wondering if it is OK to unconditionally always return -EREMCHG here. Shouldn't this depend on the return code of invalidate_inode_pages2_range() ? ret may be the value returned by mapping->a_ops->launder_page(page) instead of -EBUSY that invalidate_inode_pages2_range() otherwise returns for a failed invalidation. Isn't their any error condition that would be better served by not forcing the fallback to buffered write ? E.g. -ENOMEM ? > + 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; > + } This looks fine. This would happen only for conventional zone writes since sequential zone writes cannot ever issue direct IOs on top of cached data as that would be a forbidden "overwrite" operation. > > return zonefs_file_buffered_write(iocb, from); > } > -- Damien Le Moal Western Digital Research