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Message-ID: <4F9AC94A.3070506@sandeen.net> Date: Fri, 27 Apr 2012 11:28:58 -0500 From: Eric Sandeen <sandeen@...deen.net> To: Eric Sandeen <sandeen@...hat.com> CC: "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>, ext4 development <linux-ext4@...r.kernel.org>, Andreas Dilger <adilger@...ger.ca>, Bernd Schubert <bernd.schubert@...m.fraunhofer.de> Subject: Re: [PATCH] vfs: allow custom EOF in generic_file_llseek code On 4/27/12 11:21 AM, Eric Sandeen wrote: > For ext3/4 htree directories, using the vfs llseek function with > SEEK_END goes to i_size like for any other file, but in reality > we want the maximum possible hash value. Recent changes > in ext4 have cut & pasted generic_file_llseek() back into fs/ext4/dir.c, > but replicating this core code seems like a bad idea, especially > since the copy has already diverged from the vfs. > > This patch implements a version of generic_file_llseek which can accept > both a custom maximum offset, and a custom EOF position. With this > in place, ext4_dir_llseek can pass in the appropriate maximum hash > position for both maxsize and eof, and get what it wants. > > As far as I know, this does not fix any bugs - nfs in the kernel > doesn't use SEEK_END, and I don't know of any user who does. But > some ext4 folks seem keen on doing the right thing here, and I can't > really argue. > > (Patch also fixes up some comments slightly) > > Signed-off-by: Eric Sandeen <sandeen@...hat.com> I guess I should ahev done a patch series, although the ext4 patch is so messy it's hard to read as a patch. With the new framework in place, ext4_dir_llseek can just be: /* * ext4_dir_llseek() calls generic_file_llseek_size to handle htree * directories, where the "offset" is in terms of the filename hash * value instead of the byte offset. * * Because we may return a 64-bit hash that is well beyond offset limits, * we need to pass the max hash as the maximum allowable offset in * the htree directory case. * * For non-htree, ext4_llseek already chooses the proper max offset. */ loff_t ext4_dir_llseek(struct file *file, loff_t offset, int origin) { struct inode *inode = file->f_mapping->host; int dx_dir = is_dx_dir(inode); loff_t htree_max = ext4_get_htree_eof(file); if (likely(dx_dir)) return generic_file_llseek_size_eof(file, offset, origin, htree_max, htree_max); else return ext4_llseek(file, offset, origin); } -Eric -- 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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