On Fri, 27 Jul 2012, Lukas Czerner wrote: > Currently the allocation might happen in the punched range after the > truncation and before the releasing the space of the range. This would > lead to blocks being unallocated under the mapped buffer heads resulting > in nasty bugs. > > With this commit we take i_mutex before going to do anything in the > ext4_ext_punch_hole() preventing any write to happen while the hole > punching is in progress. This will also allow us to ditch the writeout > of dirty pages withing the range. > > This commit was based on code provided by Zheng Liu, thanks!
I'm glad you have found that i_mutex really is needed here: it had worried me that it was not taken, but I could only raise a concern, didn't really know one way or the other. > > Signed-off-by: Lukas Czerner <[email protected]> > --- > fs/ext4/extents.c | 26 ++++++++++---------------- > 1 files changed, 10 insertions(+), 16 deletions(-) > > diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c > index 91341ec..2d6a216 100644 > --- a/fs/ext4/extents.c > +++ b/fs/ext4/extents.c > @@ -4755,9 +4755,11 @@ int ext4_ext_punch_hole(struct file *file, loff_t > offset, loff_t length) > loff_t first_page_offset, last_page_offset; > int credits, err = 0; > > + mutex_lock(&inode->i_mutex); > + > /* No need to punch hole beyond i_size */ > if (offset >= inode->i_size) > - return 0; > + goto out1; Note that this is wrong, but there is no reason why it should be you to fix it in this patchset. Blocks may have been fallocated beyond i_size, and they should be removed when a hole is punched there. It's on the ext4 TODO list to be fixed, so don't worry about it: unless your changes happen to make it trivial to fix at the same time. > > /* > * If the hole extends beyond i_size, set the hole > @@ -4775,18 +4777,6 @@ int ext4_ext_punch_hole(struct file *file, loff_t > offset, loff_t length) > first_page_offset = first_page << PAGE_CACHE_SHIFT; > last_page_offset = last_page << PAGE_CACHE_SHIFT; > > - /* > - * 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; > - } > - It's not clear to me why that's now safe to remove: a little more comment in the commit would be good; but so long as it's clear to ext4 developers, don't try to make it clear to me - that would take far too long! Hugh > /* Now release the pages */ > if (last_page_offset > first_page_offset) { > truncate_pagecache_range(inode, first_page_offset, > @@ -4798,12 +4788,14 @@ int ext4_ext_punch_hole(struct file *file, loff_t > offset, loff_t length) > > credits = ext4_writepage_trans_blocks(inode); > handle = ext4_journal_start(inode, credits); > - if (IS_ERR(handle)) > - return PTR_ERR(handle); > + if (IS_ERR(handle)) { > + err = PTR_ERR(handle); > + goto out1; > + } > > err = ext4_orphan_add(handle, inode); > if (err) > - goto out; > + goto out1; > > /* > * Now we need to zero out the non-page-aligned data in the > @@ -4893,6 +4885,8 @@ out: > inode->i_mtime = inode->i_ctime = ext4_current_time(inode); > ext4_mark_inode_dirty(handle, inode); > ext4_journal_stop(handle); > +out1: > + mutex_unlock(&inode->i_mutex); > return err; > } > int ext4_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo, > -- > 1.7.7.6 -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
