gfs2: Improve mmap write vs. punch_hole consistency

When punching a hole in a file, use filemap_write_and_wait_range to
write back any dirty pages in the range of the hole.  As a side effect,
if the hole isn't page aligned, this marks unaligned pages at the
beginning and the end of the hole read-only.  This is required when the
block size is smaller than the page size: when those pages are written
to again after the hole punching, we must make sure that page_mkwrite is
called for those pages so that the page will be fully allocated and any
blocks turned into holes from the hole punching will be reallocated.
(If a page is writably mapped, page_mkwrite won't be called.)

Fixes xfstest generic/567.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

diff --git a/fs/gfs2/bmap.c b/fs/gfs2/bmap.c
index f63df54..bb0113a 100644 (file)
--- a/fs/gfs2/bmap.c
+++ b/fs/gfs2/bmap.c
@@ -2440,8 +2440,16 @@ int __gfs2_punch_hole(struct file *file, loff_t offset, loff_t length)
        struct inode *inode = file_inode(file);
        struct gfs2_inode *ip = GFS2_I(inode);
        struct gfs2_sbd *sdp = GFS2_SB(inode);
+       unsigned int blocksize = i_blocksize(inode);
+       loff_t start, end;
        int error;
 
+       start = round_down(offset, blocksize);
+       end = round_up(offset + length, blocksize) - 1;
+       error = filemap_write_and_wait_range(inode->i_mapping, start, end);
+       if (error)
+               return error;
+
        if (gfs2_is_jdata(ip))
                error = gfs2_trans_begin(sdp, RES_DINODE + 2 * RES_JDATA,
                                         GFS2_JTRUNC_REVOKES);
@@ -2455,9 +2463,8 @@ int __gfs2_punch_hole(struct file *file, loff_t offset, loff_t length)
                if (error)
                        goto out;
        } else {
-               unsigned int start_off, end_len, blocksize;
+               unsigned int start_off, end_len;
 
-               blocksize = i_blocksize(inode);
                start_off = offset & (blocksize - 1);
                end_len = (offset + length) & (blocksize - 1);
                if (start_off) {