From: Eryu Guan <eguan@xxxxxxxxxx>
commit ee70daaba82d70766d0723b743d9fdeb3b06102a upstream.
Since commit d531d91d6990 ("xfs: always use unwritten extents for
direct I/O writes"), we start allocating unwritten extents for all
direct writes to allow appending aio in XFS.
But for dio writes that could extend file size we update the in-core
inode size first, then convert the unwritten extents to real
allocations at dio completion time in xfs_dio_write_end_io(). Thus a
racing direct read could see the new i_size and find the unwritten
extents first and read zeros instead of actual data, if the direct
writer also takes a shared iolock.
Fix it by updating the in-core inode size after the unwritten extent
conversion. To do this, introduce a new boolean argument to
xfs_iomap_write_unwritten() to tell if we want to update in-core
i_size or not.
Suggested-by: Brian Foster <bfoster@xxxxxxxxxx>
Reviewed-by: Brian Foster <bfoster@xxxxxxxxxx>
Signed-off-by: Eryu Guan <eguan@xxxxxxxxxx>
Reviewed-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
[hch: backported to the old direct I/O code before Linux 4.10]
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
fs/xfs/xfs_aops.c | 25 +++++++++++++++++--------
fs/xfs/xfs_iomap.c | 7 +++++--
fs/xfs/xfs_iomap.h | 2 +-
fs/xfs/xfs_pnfs.c | 2 +-
4 files changed, 24 insertions(+), 12 deletions(-)
diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
index d23889e0bedc..2b9d7c5800ee 100644
--- a/fs/xfs/xfs_aops.c
+++ b/fs/xfs/xfs_aops.c
@@ -335,7 +335,8 @@ xfs_end_io(
error = xfs_reflink_end_cow(ip, offset, size);
break;
case XFS_IO_UNWRITTEN:
- error = xfs_iomap_write_unwritten(ip, offset, size);
+ /* writeback should never update isize */
+ error = xfs_iomap_write_unwritten(ip, offset, size, false);
break;
default:
ASSERT(!xfs_ioend_is_append(ioend) || ioend->io_append_trans);
@@ -1532,6 +1533,21 @@ xfs_end_io_direct_write(
return 0;
}
+ if (flags & XFS_DIO_FLAG_COW)
+ error = xfs_reflink_end_cow(ip, offset, size);
+
+ /*
+ * Unwritten conversion updates the in-core isize after extent
+ * conversion but before updating the on-disk size. Updating isize any
+ * earlier allows a racing dio read to find unwritten extents before
+ * they are converted.
+ */
+ if (flags & XFS_DIO_FLAG_UNWRITTEN) {
+ trace_xfs_end_io_direct_write_unwritten(ip, offset, size);
+
+ return xfs_iomap_write_unwritten(ip, offset, size, true);
+ }
+
/*
* We need to update the in-core inode size here so that we don't end up
* with the on-disk inode size being outside the in-core inode size. We
@@ -1548,13 +1564,6 @@ xfs_end_io_direct_write(
i_size_write(inode, offset + size);
spin_unlock(&ip->i_flags_lock);
- if (flags & XFS_DIO_FLAG_COW)
- error = xfs_reflink_end_cow(ip, offset, size);
- if (flags & XFS_DIO_FLAG_UNWRITTEN) {
- trace_xfs_end_io_direct_write_unwritten(ip, offset, size);
-
- error = xfs_iomap_write_unwritten(ip, offset, size);
- }
if (flags & XFS_DIO_FLAG_APPEND) {
trace_xfs_end_io_direct_write_append(ip, offset, size);
diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
index 65740d1cbd92..f286f63c430c 100644
--- a/fs/xfs/xfs_iomap.c
+++ b/fs/xfs/xfs_iomap.c
@@ -836,7 +836,8 @@ int
xfs_iomap_write_unwritten(
xfs_inode_t *ip,
xfs_off_t offset,
- xfs_off_t count)
+ xfs_off_t count,
+ bool update_isize)
{
xfs_mount_t *mp = ip->i_mount;
xfs_fileoff_t offset_fsb;
@@ -847,6 +848,7 @@ xfs_iomap_write_unwritten(
xfs_trans_t *tp;
xfs_bmbt_irec_t imap;
struct xfs_defer_ops dfops;
+ struct inode *inode = VFS_I(ip);
xfs_fsize_t i_size;
uint resblks;
int error;
@@ -906,7 +908,8 @@ xfs_iomap_write_unwritten(
i_size = XFS_FSB_TO_B(mp, offset_fsb + count_fsb);
if (i_size > offset + count)
i_size = offset + count;
-
+ if (update_isize && i_size > i_size_read(inode))
+ i_size_write(inode, i_size);
i_size = xfs_new_eof(ip, i_size);
if (i_size) {
ip->i_d.di_size = i_size;
diff --git a/fs/xfs/xfs_iomap.h b/fs/xfs/xfs_iomap.h
index 6d45cf01fcff..d71703af5c76 100644
--- a/fs/xfs/xfs_iomap.h
+++ b/fs/xfs/xfs_iomap.h
@@ -27,7 +27,7 @@ int xfs_iomap_write_direct(struct xfs_inode *, xfs_off_t, size_t,
struct xfs_bmbt_irec *, int);
int xfs_iomap_write_allocate(struct xfs_inode *, int, xfs_off_t,
struct xfs_bmbt_irec *);
-int xfs_iomap_write_unwritten(struct xfs_inode *, xfs_off_t, xfs_off_t);
+int xfs_iomap_write_unwritten(struct xfs_inode *, xfs_off_t, xfs_off_t, bool);
void xfs_bmbt_to_iomap(struct xfs_inode *, struct iomap *,
struct xfs_bmbt_irec *);
diff --git a/fs/xfs/xfs_pnfs.c b/fs/xfs/xfs_pnfs.c
index 93a7aafa56d6..cecd37569ddb 100644
--- a/fs/xfs/xfs_pnfs.c
+++ b/fs/xfs/xfs_pnfs.c
@@ -279,7 +279,7 @@ xfs_fs_commit_blocks(
(end - 1) >> PAGE_SHIFT);
WARN_ON_ONCE(error);
- error = xfs_iomap_write_unwritten(ip, start, length);
+ error = xfs_iomap_write_unwritten(ip, start, length, false);
if (error)
goto out_drop_iolock;
}
--
2.14.2