This patch addresses a bug found by xfstests 75, 112, 127
when blocksize = 1k
This bug happens because the punch hole code only zeros
out non block aligned regions of the page. This means that if the
blocks are smaller than a page, then the block aligned regions of
the page inside the hole are left un-zeroed, and their buffer heads
are still mapped. This bug is corrected by using
ext4_discard_partial_page_buffers to properly zero the partial page
at the head and tail of the hole, and unmap the corresponding buffer
heads
Signed-off-by: Allison Henderson <achender@xxxxxxxxxxxxxxxxxx>
---
:100644 100644 4d73e11... cd58117... M fs/ext4/extents.c
fs/ext4/extents.c | 48 ++++++++++++++++++++++++++++++------------------
1 files changed, 30 insertions(+), 18 deletions(-)
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 4d73e11..cd58117 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -4157,7 +4157,7 @@ int ext4_ext_punch_hole(struct file *file, loff_t offset, loff_t length)
struct address_space *mapping = inode->i_mapping;
struct ext4_map_blocks map;
handle_t *handle;
- loff_t first_block_offset, last_block_offset, block_len;
+ loff_t first_block_offset, last_block_offset, page_len;
loff_t first_page, last_page, first_page_offset, last_page_offset;
int ret, credits, blocks_released, err = 0;
@@ -4206,24 +4206,36 @@ int ext4_ext_punch_hole(struct file *file, loff_t offset, loff_t length)
goto out;
/*
- * Now we need to zero out the un block aligned data.
- * If the file is smaller than a block, just
- * zero out the middle
+ * Now we need to zero out the non-page-aligned data in the
+ * pages at the start and tail of the hole, and unmap the buffer
+ * heads for the block aligned regions of the page that were
+ * completely zeroed.
*/
- if (first_block > last_block)
- ext4_block_zero_page_range(handle, mapping, offset, length);
- else {
- /* zero out the head of the hole before the first block */
- block_len = first_block_offset - offset;
- if (block_len > 0)
- ext4_block_zero_page_range(handle, mapping,
- offset, block_len);
-
- /* zero out the tail of the hole after the last block */
- block_len = offset + length - last_block_offset;
- if (block_len > 0) {
- ext4_block_zero_page_range(handle, mapping,
- last_block_offset, block_len);
+ if (first_page > last_page) {
+ /*
+ * If the file space being truncated is contained within a page
+ * just zero out and unmap the middle of that page
+ */
+ ext4_discard_partial_page_buffers(handle,
+ mapping, offset, length, 0);
+ } else {
+ /*
+ * zero out and unmap the partial page that contains
+ * the start of the hole
+ */
+ page_len = first_page_offset - offset;
+ if (page_len > 0)
+ ext4_discard_partial_page_buffers(handle, mapping,
+ offset, page_len, 0);
+
+ /*
+ * zero out and unmap the partial page that contains
+ * the end of the hole
+ */
+ page_len = offset + length - last_page_offset;
+ if (page_len > 0) {
+ ext4_discard_partial_page_buffers(handle, mapping,
+ last_page_offset, page_len, 0);
}
}
--
1.7.1
--
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