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Message-ID: <20140530232633.GE17413@birch.djwong.org> Date: Fri, 30 May 2014 16:26:33 -0700 From: "Darrick J. Wong" <darrick.wong@...cle.com> To: Andreas Dilger <adilger@...ger.ca> Cc: "Theodore Ts'o" <tytso@....edu>, Zheng Liu <gnehzuil.liu@...il.com>, "linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>, Ian Nartowicz <claws@...towicz.co.uk>, Tao Ma <tm@....ma>, Andreas Dilger <adilger.kernel@...ger.ca>, Zheng Liu <wenqing.lz@...bao.com> Subject: Re: [RFC][PATCH] ext4: handle fast symlink properly with inline_data On Tue, Feb 18, 2014 at 11:07:24AM -0800, Andreas Dilger wrote: > I suspect that the stats for symlinks > 60 but < ~150 chars is only a very > small fraction of files. If the code complexity of handling this is very > small (i.e. it is just handled as a natural consequence of writing "data" > of this size) then I would be OK with it. > > Otherwise, I expect the code and maintenance overhead of supporting > the 0.01% (?) of symlinks that are this size is probably lot worth it. > > People could check what the actual usage is via the "fsstats" tool at: > > http://www.pdsi-scidac.org/fsstats/ > > There is also data there already that reports stats on symlink length, but > it is mostly HPC filesystems and it might be better to redo this with a > desktop-type workload. I think we should either put in this kernel patch so that we can read inline data fast symlinks, or remove the ability to write inline data fast symlinks. It's a bit surprising that I can do: # mke2fs -t ext4 -O inline_data /dev/sdb # mount /dev/sdb /mnt/ # ln -s "Fuzzy Wuzzy was a bear. Fuzzy Wuzzy had no hair. I guess he wasn't fuzzy, was he?" /mnt/biglink # readlink /mnt/biglink Fuzzy Wuzzy was a bear. Fuzzy Wuzzy had no hair. I guess he wasn't fuzzy, was he? # umount /mnt # mount /dev/sdb /mnt/ # readlink /mnt/biglink Fuzzy Wuzzy was a bear. Fuzzy Wuzzy had no hair. I guess he What happened to the punchline of the limerick? ------------^^^^^^^ ???? :) e2fsck still seems to think that you can't have inline_data fast symlinks. I don't see a downside to continuing to allow them. --D > > Cheers, Andreas > > >> On Feb 17, 2014, at 17:52, Theodore Ts'o <tytso@....edu> wrote: > >> > >> On Thu, Feb 13, 2014 at 03:07:17PM +0800, Zheng Liu wrote: > >> > >> I am not sure whether or not we need to enable inline_data for a fast > >> symlink inode. Obviously, it brings a benefit that after enabling > >> inline_data feature for a fast symlink we can get more space to store > >> the path. But it seems that the original patch doesn't want to do this > >> Another solution for fixing this bug is to disable inline_data for a > >> fast symlink. Any comment? > > > > Well, if we are using inline data, and we have a symlink which is > > longer than 60 bytes, but less than extra space available for an > > inline data, it seems like a good thing to support. > > > > The downside is that it is a bit more complication to add the kernel's > > code in both the kernel as well as e2fsprogs, but it doesn't seem that > > bad. > > > > So I don't have any objections to adding this functionality. What do > > other folks think? > > > > - Ted > -- > To unsubscribe from this list: send the line "unsubscribe linux-ext4" in > the body of a message to majordomo@...r.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@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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