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/extents.c b/fs/ext4/extents.c
index 9c6d06d..d58365e 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -2599,8 +2599,8 @@
return 1;
}
-static int ext4_ext_remove_space(struct inode *inode, ext4_lblk_t start,
- ext4_lblk_t end)
+int ext4_ext_remove_space(struct inode *inode, ext4_lblk_t start,
+ ext4_lblk_t end)
{
struct super_block *sb = inode->i_sb;
int depth = ext_depth(inode);
@@ -4623,187 +4623,6 @@
return (error < 0 ? error : 0);
}
-/*
- * ext4_ext_punch_hole
- *
- * Punches a hole of "length" bytes in a file starting
- * at byte "offset"
- *
- * @inode: The inode of the file to punch a hole in
- * @offset: The starting byte offset of the hole
- * @length: The length of the hole
- *
- * Returns the number of blocks removed or negative on err
- */
-int ext4_ext_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;
- handle_t *handle;
- loff_t first_page, last_page, page_len;
- loff_t first_page_offset, last_page_offset;
- int credits, err = 0;
-
- /*
- * Write out all dirty pages to avoid race conditions
- * Then release them.
- */
- if (mapping->nrpages && mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) {
- err = filemap_write_and_wait_range(mapping,
- offset, offset + length - 1);
-
- if (err)
- return err;
- }
-
- mutex_lock(&inode->i_mutex);
- /* It's not possible punch hole on append only file */
- if (IS_APPEND(inode) || IS_IMMUTABLE(inode)) {
- err = -EPERM;
- goto out_mutex;
- }
- if (IS_SWAPFILE(inode)) {
- err = -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);
- err = ext4_flush_unwritten_io(inode);
- if (err)
- goto out_dio;
- inode_dio_wait(inode);
-
- credits = ext4_writepage_trans_blocks(inode);
- handle = ext4_journal_start(inode, EXT4_HT_TRUNCATE, credits);
- if (IS_ERR(handle)) {
- err = PTR_ERR(handle);
- 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
- */
- err = ext4_discard_partial_page_buffers(handle,
- mapping, offset, length, 0);
-
- if (err)
- goto out;
- } 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) {
- err = ext4_discard_partial_page_buffers(handle, mapping,
- offset, page_len, 0);
- if (err)
- goto out;
- }
-
- /*
- * 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) {
- err = ext4_discard_partial_page_buffers(handle, mapping,
- last_page_offset, page_len, 0);
- if (err)
- goto out;
- }
- }
-
- /*
- * 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) {
- err = ext4_discard_partial_page_buffers(handle,
- mapping, inode->i_size, page_len, 0);
-
- if (err)
- goto out;
- }
- }
-
- 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;
-
- down_write(&EXT4_I(inode)->i_data_sem);
- ext4_discard_preallocations(inode);
-
- err = ext4_es_remove_extent(inode, first_block,
- stop_block - first_block);
- err = ext4_ext_remove_space(inode, first_block, stop_block - 1);
-
- ext4_discard_preallocations(inode);
-
- if (IS_SYNC(inode))
- ext4_handle_sync(handle);
-
- up_write(&EXT4_I(inode)->i_data_sem);
-
-out:
- inode->i_mtime = inode->i_ctime = ext4_current_time(inode);
- ext4_mark_inode_dirty(handle, inode);
- ext4_journal_stop(handle);
-out_dio:
- ext4_inode_resume_unlocked_dio(inode);
-out_mutex:
- mutex_unlock(&inode->i_mutex);
- return err;
-}
-
int ext4_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
__u64 start, __u64 len)
{