From patchwork Fri Aug 28 18:42:59 2009 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Subject: Question on fallocate/ftruncate sequence From: Jiaying Zhang X-Patchwork-Id: 32401 Message-Id: <5df78e1d0908281142r683b902ube65288df858695d@mail.gmail.com> To: Frank Mayhar Cc: Andreas Dilger , Eric Sandeen , Curt Wohlgemuth , ext4 development Date: Fri, 28 Aug 2009 11:42:59 -0700 Sorry for joining the conversation late. Frank and I had a discussion on this problem this morning. We wonder whether we can just add the checking on whether i_blocks is consistent with i_size during truncate. Here is the patch I tried and it seems to have solved the problem. I.e., the space reserved in fallocate(KEEP_SIZE) is now freed in the next truncate. One thing I am not sure is whether adding this check in inode_setattr may cause any problem in other cases. I saw inode_setattr is called at many places as well as during ftruncate. Any opinions on this proposed solution? Jiaying On Thu, Jul 23, 2009 at 3:46 PM, Frank Mayhar wrote: > On Thu, 2009-07-23 at 15:56 -0600, Andreas Dilger wrote: >> On Jul 23, 2009  11:05 -0700, Frank Mayhar wrote: >> > On Thu, 2009-07-23 at 12:00 -0500, Eric Sandeen wrote: >> > > Sorry I skimmed to fast, skipped over the fsck part.  But: >> > > >> > > # touch /mnt/test/testfile >> > > # /root/fallocate -n -l 16m /mnt/test/testfile >> > > # ls -l /mnt/test/testfile >> > > -rw-r--r-- 1 root root 0 Jul 23 12:13 /mnt/test/testfile >> > > # du -h /mnt/test/testfile >> > > 16M       /mnt/test/testfile >> > > >> > > there doesn't seem to be a problem in fsck w/ block past EOF, or am I >> > > missing something else? >> > >> > I was taking Andreas' word for it but now that you mention it, I see the >> > same thing.  Andreas, did you have a specific case in mind? >> >> Ted and I had discussed this in the past, maybe he fixed e2fsck to not >> change the file size when there are blocks allocated beyond EOF.  Having >> a flag wouldn't be a terrible idea, IMHO, so that e2fsck can make a >> better decision on whether the size or the blocks count are more correct. >> I'm not dead set on it. > > For the moment I'm going to table the e2fsck change and make the flag > memory-only.  It'll be easy enough to change this if and when you guys > come to an agreement about what is right. > > As for the flag itself, I'll pick a bit that doesn't conflict with > anything else and leave reconciling the already-conflicting bits to you > guys. > -- > Frank Mayhar > Google, Inc. > > -- > To unsubscribe from this list: send the line "unsubscribe linux-ext4" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at  http://vger.kernel.org/majordomo-info.html > --- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html --- git-linux/fs/attr.c 2009-05-20 18:05:55.000000000 -0700 +++ linux-2.6.30.5/fs/attr.c 2009-08-27 14:34:48.000000000 -0700 @@ -68,7 +68,8 @@ int inode_setattr(struct inode * inode, unsigned int ia_valid = attr->ia_valid; if (ia_valid & ATTR_SIZE && - attr->ia_size != i_size_read(inode)) { + (attr->ia_size != i_size_read(inode) || + attr->ia_size >> 9 < inode->i_blocks - 1)) { int error = vmtruncate(inode, attr->ia_size); if (error) return error;