The problem is that we need to split extents at the eof block
so that the existing zeroing actually takes effect. The patch below
fixes the test case for me:
diff --git a/fs/iomap.c b/fs/iomap.c
index e8f1bcdc95cf..9c88b8736de0 100644
--- a/fs/iomap.c
+++ b/fs/iomap.c
@@ -143,13 +143,20 @@ static void
iomap_adjust_read_range(struct inode *inode, struct iomap_page *iop,
loff_t *pos, loff_t length, unsigned *offp, unsigned *lenp)
{
+ unsigned block_bits = inode->i_blkbits;
+ unsigned block_size = (1 << block_bits);
unsigned poff = *pos & (PAGE_SIZE - 1);
unsigned plen = min_t(loff_t, PAGE_SIZE - poff, length);
+ unsigned first = poff >> block_bits;
+ unsigned last = (poff + plen - 1) >> block_bits;
+ unsigned end = (i_size_read(inode) & (PAGE_SIZE - 1)) >> block_bits;
+ /*
+ * If the block size is smaller than the page size we need to check the
+ * per-block uptodate status and adjust the offset and length if needed
+ * to avoid reading in already uptodate ranges.
+ */
if (iop) {
- unsigned block_size = i_blocksize(inode);
- unsigned first = poff >> inode->i_blkbits;
- unsigned last = (poff + plen - 1) >> inode->i_blkbits;
unsigned int i;
/* move forward for each leading block marked uptodate */
@@ -159,17 +166,27 @@ iomap_adjust_read_range(struct inode *inode, struct iomap_page *iop,
*pos += block_size;
poff += block_size;
plen -= block_size;
+ first++;
}
/* truncate len if we find any trailing uptodate block(s) */
for ( ; i <= last; i++) {
if (test_bit(i, iop->uptodate)) {
plen -= (last - i + 1) * block_size;
+ last = i - 1;
break;
}
}
}
+ /*
+ * If the extent spans the block that contains the i_size we need to
+ * handle both halves separately so that we properly zero data in the
+ * page cache for blocks that are entirely outside of i_size.
+ */
+ if (first <= end && last > end)
+ plen -= (last - end) * block_size;
+
*offp = poff;
*lenp = plen;
}
