xfs: update i_size after unwritten conversion in dio completion

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@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Eryu Guan <eguan@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
[hch: backported to the old direct I/O code before Linux 4.10]
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
index d23889e0bedccf9cd51492d83819e7c1926e09a3..2b9d7c5800eeba7dc7f8f882a8e37422d63659db 100644 (file)
--- 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 65740d1cbd92d76b32989c832b4b5922123fbae0..f286f63c430c0ec76baa39288f3a946c1a32818b 100644 (file)
--- 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 6d45cf01fcffb01e123cb75d3a2707318c4cac31..d71703af5c76800980b4e04539bc0fb22e7b02fc 100644 (file)
--- 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 93a7aafa56d6fdd9b76246f4e5c3196fdc17f985..cecd37569ddb30d624b163bf8dab3338bcfa75f7 100644 (file)
--- 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;
        }