Re: [Ext2-devel] [PATCH] concurrent block allocation for ext2 against 2.5.64

[Alex Tomas]

fs/attr.c:
        if (ia_valid & ATTR_SIZE) {
                if (attr->ia_size == inode->i_size) {
                        if (ia_valid == ATTR_SIZE)
                                goto out;       /* we can skip lock_kernel() */
                } else {
                        lock_kernel();
                        error = vmtruncate(inode, attr->ia_size);
                        unlock_kernel();
                        if (error)
                                goto out;
                }
        }

so, all (!) truncates are serialized

>>>>> Andreas Dilger (AD) writes:

 AD> On Mar 13, 2003 11:55 +0300, Alex Tomas wrote:
 >> as Andrew said, concurrent balloc for ext3 is useless because of
 >> BKL.  and I saw it in benchmarks. but it may be useful for ext2.

 AD> Sadly, we are constantly diverging the ext2/ext3 codebases.  Lots
 AD> of features are going into ext3, but lots of fixes/improvements
 AD> are only going into ext2.  Is ext3 holding BKL for doing
 AD> journal_start() still?

 AD> Looking at ext3_prepare_write() we grab the BKL for doing
 AD> journal_start() and for journal_stop(), but I don't _think_ we
 AD> need BKL for journal_stop() do we?  We may or may not need it for
 AD> the journal_data case, but that is not even working right now I
 AD> think.

 AD> It also seems we are getting BKL in ext3_truncate(), which likely
 AD> isn't needed past journal_start(), although we do need to have
 AD> superblock-only lock for ext3_orphan_add/del.