ext4: refactor punch hole code
Move common code in ext4_ind_punch_hole() and ext4_ext_punch_hole()
into ext4_punch_hole(). This saves over 150 lines of code.
This also fixes a potential bug when the punch_hole() code is racing
against indirect-to-extents or extents-to-indirect migation. We are
currently using i_mutex to protect against changes to the inode flag;
specifically, the append-only, immutable, and extents inode flags. So
we need to take i_mutex before deciding whether to use the
extents-specific or indirect-specific punch_hole code.
Also, there was a missing call to ext4_inode_block_unlocked_dio() in
the indirect punch codepath. This was added in commit 02d262dffcf4c
to block DIO readers racing against the punch operation in the
codepath for extent-mapped inodes, but it was missing for
indirect-block mapped inodes. One of the advantages of refactoring
the code is that it makes such oversights much less likely.
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index a4ffb47..9bda50a 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3566,20 +3566,190 @@
int ext4_punch_hole(struct file *file, loff_t offset, loff_t length)
{
struct inode *inode = file_inode(file);
+ struct super_block *sb = inode->i_sb;
+ ext4_lblk_t first_block, stop_block;
+ struct address_space *mapping = inode->i_mapping;
+ loff_t first_page, last_page, page_len;
+ loff_t first_page_offset, last_page_offset;
+ handle_t *handle;
+ unsigned int credits;
+ int ret = 0;
+
if (!S_ISREG(inode->i_mode))
return -EOPNOTSUPP;
- if (!ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))
- return ext4_ind_punch_hole(file, offset, length);
-
- if (EXT4_SB(inode->i_sb)->s_cluster_ratio > 1) {
+ if (EXT4_SB(sb)->s_cluster_ratio > 1) {
/* TODO: Add support for bigalloc file systems */
return -EOPNOTSUPP;
}
trace_ext4_punch_hole(inode, offset, length);
- return ext4_ext_punch_hole(file, offset, length);
+ /*
+ * Write out all dirty pages to avoid race conditions
+ * Then release them.
+ */
+ if (mapping->nrpages && mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) {
+ ret = filemap_write_and_wait_range(mapping, offset,
+ offset + length - 1);
+ if (ret)
+ return ret;
+ }
+
+ mutex_lock(&inode->i_mutex);
+ /* It's not possible punch hole on append only file */
+ if (IS_APPEND(inode) || IS_IMMUTABLE(inode)) {
+ ret = -EPERM;
+ goto out_mutex;
+ }
+ if (IS_SWAPFILE(inode)) {
+ ret = -ETXTBSY;
+ goto out_mutex;
+ }
+
+ /* No need to punch hole beyond i_size */
+ if (offset >= inode->i_size)
+ goto out_mutex;
+
+ /*
+ * If the hole extends beyond i_size, set the hole
+ * to end after the page that contains i_size
+ */
+ if (offset + length > inode->i_size) {
+ length = inode->i_size +
+ PAGE_CACHE_SIZE - (inode->i_size & (PAGE_CACHE_SIZE - 1)) -
+ offset;
+ }
+
+ first_page = (offset + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
+ last_page = (offset + length) >> PAGE_CACHE_SHIFT;
+
+ first_page_offset = first_page << PAGE_CACHE_SHIFT;
+ last_page_offset = last_page << PAGE_CACHE_SHIFT;
+
+ /* Now release the pages */
+ if (last_page_offset > first_page_offset) {
+ truncate_pagecache_range(inode, first_page_offset,
+ last_page_offset - 1);
+ }
+
+ /* Wait all existing dio workers, newcomers will block on i_mutex */
+ ext4_inode_block_unlocked_dio(inode);
+ ret = ext4_flush_unwritten_io(inode);
+ if (ret)
+ goto out_dio;
+ inode_dio_wait(inode);
+
+ if (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))
+ credits = ext4_writepage_trans_blocks(inode);
+ else
+ credits = ext4_blocks_for_truncate(inode);
+ handle = ext4_journal_start(inode, EXT4_HT_TRUNCATE, credits);
+ if (IS_ERR(handle)) {
+ ret = PTR_ERR(handle);
+ ext4_std_error(sb, ret);
+ goto out_dio;
+ }
+
+ /*
+ * 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_page > last_page) {
+ /*
+ * If the file space being truncated is contained
+ * within a page just zero out and unmap the middle of
+ * that page
+ */
+ ret = ext4_discard_partial_page_buffers(handle,
+ mapping, offset, length, 0);
+
+ if (ret)
+ goto out_stop;
+ } 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) {
+ ret = ext4_discard_partial_page_buffers(handle, mapping,
+ offset, page_len, 0);
+ if (ret)
+ goto out_stop;
+ }
+
+ /*
+ * 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) {
+ ret = ext4_discard_partial_page_buffers(handle, mapping,
+ last_page_offset, page_len, 0);
+ if (ret)
+ goto out_stop;
+ }
+ }
+
+ /*
+ * If i_size is contained in the last page, we need to
+ * unmap and zero the partial page after i_size
+ */
+ if (inode->i_size >> PAGE_CACHE_SHIFT == last_page &&
+ inode->i_size % PAGE_CACHE_SIZE != 0) {
+ page_len = PAGE_CACHE_SIZE -
+ (inode->i_size & (PAGE_CACHE_SIZE - 1));
+
+ if (page_len > 0) {
+ ret = ext4_discard_partial_page_buffers(handle,
+ mapping, inode->i_size, page_len, 0);
+
+ if (ret)
+ goto out_stop;
+ }
+ }
+
+ first_block = (offset + sb->s_blocksize - 1) >>
+ EXT4_BLOCK_SIZE_BITS(sb);
+ stop_block = (offset + length) >> EXT4_BLOCK_SIZE_BITS(sb);
+
+ /* If there are no blocks to remove, return now */
+ if (first_block >= stop_block)
+ goto out_stop;
+
+ down_write(&EXT4_I(inode)->i_data_sem);
+ ext4_discard_preallocations(inode);
+
+ ret = ext4_es_remove_extent(inode, first_block,
+ stop_block - first_block);
+ if (ret) {
+ up_write(&EXT4_I(inode)->i_data_sem);
+ goto out_stop;
+ }
+
+ if (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))
+ ret = ext4_ext_remove_space(inode, first_block,
+ stop_block - 1);
+ else
+ ret = ext4_free_hole_blocks(handle, inode, first_block,
+ stop_block);
+
+ ext4_discard_preallocations(inode);
+ if (IS_SYNC(inode))
+ ext4_handle_sync(handle);
+ up_write(&EXT4_I(inode)->i_data_sem);
+ inode->i_mtime = inode->i_ctime = ext4_current_time(inode);
+ ext4_mark_inode_dirty(handle, inode);
+out_stop:
+ ext4_journal_stop(handle);
+out_dio:
+ ext4_inode_resume_unlocked_dio(inode);
+out_mutex:
+ mutex_unlock(&inode->i_mutex);
+ return ret;
}
/*