Currently we don't overwrite the flags field in the iomap in
xfs_bmbt_to_iomap.  This works fine with 0-initialized iomaps on stack,
but is harmful once we want to be able to reuse an iomap in the
writeback code.  Replace the shared paramter with a set of initial
flags an thus ensures the flags field is always reinitialized.

Signed-off-by: Christoph Hellwig <h...@lst.de>
Reviewed-by: Darrick J. Wong <darrick.w...@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.w...@oracle.com>
---
 fs/xfs/xfs_iomap.c | 28 +++++++++++++++++-----------
 fs/xfs/xfs_iomap.h |  2 +-
 fs/xfs/xfs_pnfs.c  |  2 +-
 3 files changed, 19 insertions(+), 13 deletions(-)

diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
index 2dc0f182f125..c0a492353826 100644
--- a/fs/xfs/xfs_iomap.c
+++ b/fs/xfs/xfs_iomap.c
@@ -54,7 +54,7 @@ xfs_bmbt_to_iomap(
        struct xfs_inode        *ip,
        struct iomap            *iomap,
        struct xfs_bmbt_irec    *imap,
-       bool                    shared)
+       u16                     flags)
 {
        struct xfs_mount        *mp = ip->i_mount;
 
@@ -79,12 +79,11 @@ xfs_bmbt_to_iomap(
        iomap->length = XFS_FSB_TO_B(mp, imap->br_blockcount);
        iomap->bdev = xfs_find_bdev_for_inode(VFS_I(ip));
        iomap->dax_dev = xfs_find_daxdev_for_inode(VFS_I(ip));
+       iomap->flags = flags;
 
        if (xfs_ipincount(ip) &&
            (ip->i_itemp->ili_fsync_fields & ~XFS_ILOG_TIMESTAMP))
                iomap->flags |= IOMAP_F_DIRTY;
-       if (shared)
-               iomap->flags |= IOMAP_F_SHARED;
        return 0;
 }
 
@@ -540,6 +539,7 @@ xfs_file_iomap_begin_delay(
        struct xfs_iext_cursor  icur, ccur;
        xfs_fsblock_t           prealloc_blocks = 0;
        bool                    eof = false, cow_eof = false, shared = false;
+       u16                     iomap_flags = 0;
        int                     whichfork = XFS_DATA_FORK;
        int                     error = 0;
 
@@ -708,7 +708,7 @@ xfs_file_iomap_begin_delay(
         * them out if the write happens to fail.
         */
        if (whichfork == XFS_DATA_FORK) {
-               iomap->flags |= IOMAP_F_NEW;
+               iomap_flags |= IOMAP_F_NEW;
                trace_xfs_iomap_alloc(ip, offset, count, whichfork, &imap);
        } else {
                trace_xfs_iomap_alloc(ip, offset, count, whichfork, &cmap);
@@ -718,14 +718,17 @@ xfs_file_iomap_begin_delay(
                if (imap.br_startoff > offset_fsb) {
                        xfs_trim_extent(&cmap, offset_fsb,
                                        imap.br_startoff - offset_fsb);
-                       error = xfs_bmbt_to_iomap(ip, iomap, &cmap, true);
+                       error = xfs_bmbt_to_iomap(ip, iomap, &cmap,
+                                       IOMAP_F_SHARED);
                        goto out_unlock;
                }
                /* ensure we only report blocks we have a reservation for */
                xfs_trim_extent(&imap, cmap.br_startoff, cmap.br_blockcount);
                shared = true;
        }
-       error = xfs_bmbt_to_iomap(ip, iomap, &imap, shared);
+       if (shared)
+               iomap_flags |= IOMAP_F_SHARED;
+       error = xfs_bmbt_to_iomap(ip, iomap, &imap, iomap_flags);
 out_unlock:
        xfs_iunlock(ip, XFS_ILOCK_EXCL);
        return error;
@@ -933,6 +936,7 @@ xfs_file_iomap_begin(
        xfs_fileoff_t           offset_fsb, end_fsb;
        int                     nimaps = 1, error = 0;
        bool                    shared = false;
+       u16                     iomap_flags = 0;
        unsigned                lockmode;
 
        if (XFS_FORCED_SHUTDOWN(mp))
@@ -1048,11 +1052,13 @@ xfs_file_iomap_begin(
        if (error)
                return error;
 
-       iomap->flags |= IOMAP_F_NEW;
+       iomap_flags |= IOMAP_F_NEW;
        trace_xfs_iomap_alloc(ip, offset, length, XFS_DATA_FORK, &imap);
 
 out_finish:
-       return xfs_bmbt_to_iomap(ip, iomap, &imap, shared);
+       if (shared)
+               iomap_flags |= IOMAP_F_SHARED;
+       return xfs_bmbt_to_iomap(ip, iomap, &imap, iomap_flags);
 
 out_found:
        ASSERT(nimaps);
@@ -1196,7 +1202,7 @@ xfs_seek_iomap_begin(
                if (data_fsb < cow_fsb + cmap.br_blockcount)
                        end_fsb = min(end_fsb, data_fsb);
                xfs_trim_extent(&cmap, offset_fsb, end_fsb);
-               error = xfs_bmbt_to_iomap(ip, iomap, &cmap, true);
+               error = xfs_bmbt_to_iomap(ip, iomap, &cmap, IOMAP_F_SHARED);
                /*
                 * This is a COW extent, so we must probe the page cache
                 * because there could be dirty page cache being backed
@@ -1218,7 +1224,7 @@ xfs_seek_iomap_begin(
        imap.br_state = XFS_EXT_NORM;
 done:
        xfs_trim_extent(&imap, offset_fsb, end_fsb);
-       error = xfs_bmbt_to_iomap(ip, iomap, &imap, false);
+       error = xfs_bmbt_to_iomap(ip, iomap, &imap, 0);
 out_unlock:
        xfs_iunlock(ip, lockmode);
        return error;
@@ -1264,7 +1270,7 @@ xfs_xattr_iomap_begin(
        if (error)
                return error;
        ASSERT(nimaps);
-       return xfs_bmbt_to_iomap(ip, iomap, &imap, false);
+       return xfs_bmbt_to_iomap(ip, iomap, &imap, 0);
 }
 
 const struct iomap_ops xfs_xattr_iomap_ops = {
diff --git a/fs/xfs/xfs_iomap.h b/fs/xfs/xfs_iomap.h
index 5c2f6aa6d78f..71d0ae460c44 100644
--- a/fs/xfs/xfs_iomap.h
+++ b/fs/xfs/xfs_iomap.h
@@ -16,7 +16,7 @@ int xfs_iomap_write_direct(struct xfs_inode *, xfs_off_t, 
size_t,
 int xfs_iomap_write_unwritten(struct xfs_inode *, xfs_off_t, xfs_off_t, bool);
 
 int xfs_bmbt_to_iomap(struct xfs_inode *, struct iomap *,
-               struct xfs_bmbt_irec *, bool shared);
+               struct xfs_bmbt_irec *, u16);
 xfs_extlen_t xfs_eof_alignment(struct xfs_inode *ip, xfs_extlen_t extsize);
 
 static inline xfs_filblks_t
diff --git a/fs/xfs/xfs_pnfs.c b/fs/xfs/xfs_pnfs.c
index a339bd5fa260..9c96493be9e0 100644
--- a/fs/xfs/xfs_pnfs.c
+++ b/fs/xfs/xfs_pnfs.c
@@ -178,7 +178,7 @@ xfs_fs_map_blocks(
        }
        xfs_iunlock(ip, XFS_IOLOCK_EXCL);
 
-       error = xfs_bmbt_to_iomap(ip, iomap, &imap, false);
+       error = xfs_bmbt_to_iomap(ip, iomap, &imap, 0);
        *device_generation = mp->m_generation;
        return error;
 out_unlock:
-- 
2.20.1

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