| Message ID | 20200713074633.875946-3-hch@lst.de |
|---|---|
| State | Not Applicable |
| Headers | show |
| Series | [1/2] iomap: Only invalidate page cache pages on direct IO writes | expand |
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. Is that the right approach though? I don't have a full picture in my head, but wouldn't we be better off marking these pages as !Uptodate and doing the direct I/O?
On 9:46 13/07, 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> Thanks. This will help btrfs. The current next tree contains the iomap changes I recomended and would need to be reverted in order to incorporate this. Once this is in the next tree I will (re)format the btrfs iomap dio patches. Reviewed-by: Goldwyn Rodrigues <rgoldwyn@suse.com> > --- > 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; > + 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 >
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 >
On Mon, Jul 13, 2020 at 07:20:50AM -0500, Goldwyn Rodrigues wrote: > On 9:46 13/07, 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> > > Thanks. This will help btrfs. The current next tree contains the iomap > changes I recomended and would need to be reverted in order to > incorporate this. Once this is in the next tree I will (re)format the > btrfs iomap dio patches. Patches in next don't need to be reverted, if you put together a branch with any iomap or other prep patches + btrfs iomap-dio I'll replace it in the for-next snapshot I push.
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 <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; 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); > } >
On Mon, Jul 13, 2020 at 12:55:09PM +0100, Matthew Wilcox wrote: > 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. > > Is that the right approach though? I don't have a full picture in my head, > but wouldn't we be better off marking these pages as !Uptodate and doing > the direct I/O? Isn't that a problem if e.g. pages are mapped into userspace and mlocked?
On Mon, Jul 13, 2020 at 08:39:20AM -0700, Darrick J. Wong wrote: > -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. Sure, I can switch the error code.
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; + 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); }
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(-)