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<p class="MsoNormal"><span style="mso-fareast-language:EN-US">Hello Amar, Xavi<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b>Von:</b> Amar Tumballi [mailto:atumball@redhat.com] <br>
<b>Gesendet:</b> Mittwoch, 10. Januar 2018 14:16<br>
<b>An:</b> Xavi Hernandez <jahernan@redhat.com>; David Spisla <david.spisla@iternity.com><br>
<b>Cc:</b> gluster-devel@gluster.org<br>
<b>Betreff:</b> Re: [Gluster-devel] Simulating some kind of "virtual file"<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Check the files in $mountpoint/.meta/ directory. These are all virtual. And meta xlator gives a very good idea about how to handle virtual files (and directories).<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">-Amar<o:p></o:p></p>
<p class="MsoNormal"><b><i>[David Spisla] Sounds good. Thank you</i></b><o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">On Wed, Jan 10, 2018 at 6:36 PM, Xavi Hernandez <<a href="mailto:jahernan@redhat.com" target="_blank">jahernan@redhat.com</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal">Hi David,<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">On Wed, Jan 10, 2018 at 1:42 PM, David Spisla <<a href="mailto:david.spisla@iternity.com" target="_blank">david.spisla@iternity.com</a>> wrote: <o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><b><i>[David Spisla] I tried this:</i></b><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><i>char *new_path = malloc(1+len_path-5);</i><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><i>memcpy(new_path, loc->path, len_path-5);</i><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><i>new_path[strlen(new_path)] = '\0';</i><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><i>loc->name = new_path + (len_path - len_name);</i><o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">First of all, you should always use memory allocation functions from gluster. This includes GF_MALLOC(), gf_strdup(), gf_asprintf() and several other variants. You can look at libglusterfs/src/mem-pool.h
to see all available options.<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">The second problem I see is that memcpy() doesn't write a terminating null character, so when you compute strlen() afterwards, it will return invalid length, or even try to access
invalid memory, causing a crash.<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">You should do something like this (assuming both loc->path and loc->name are not NULL and skipping many necessary checks):<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-family:"Courier New"">len_path = strlen(loc->path);</span><o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-family:"Courier New"">len_name = strlen(loc->name);</span><o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-family:"Courier New"">new_path = GF_MALLOC(len_path - 4, gf_common_mt_char);</span><o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-family:"Courier New"">memcpy(new_path, loc->path, len_path - 5);</span><o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-family:"Courier New"">new_path[len_path - 5] = 0;</span><o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-family:"Courier New"">loc->name = new_path + len_path - len_name;</span><o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-family:"Arial",sans-serif">This should work fine.</span><o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-family:"Arial",sans-serif">Xavi</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><b><i>[David Spisla] Yes, this worls fine. Thank you
</i></b><b><i><span style="font-family:"Segoe UI Emoji",sans-serif">😊</span>. By the way, is there a way inside gluster xlator to get access to xattr or attr of a file. In the lookup function there is only the struct loc, but I am missing there the files gfid.
It seems to be null always. I could use syncop_getxattr() with the parameter loc, but the gfid is missing. Can I get the gfid if I have only loc->path and loc-> name? It is like a conversion from files path to files gfid.</i></b><o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">One of the main purposes of the 'lookup' fop is to resolve a given path to an existing gfid, so you won't find any gfid in the lookup request (unless it's a revalidate request). You need to look at the response (cbk) of the lookup to get
the real gfid. If the request succeeds, you can find the gfid in buf->ia_gfid of the lookup callback.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Other fops that receive a loc_t structure are normally called after a successful lookup, so loc->gfid and/or loc->inode->gfid should be set (unfortunately there isn't an homogeneous management of loc_t structures by xlators, so not always
both fields are set).<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">You can also request additional xattrs in the lookup request by adding them to the xdata dictionary. Their values will be returned in the xdata argument of the lookup callback.<o:p></o:p></p>
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<p class="MsoNormal"><span style="color:#888888">Xavi<o:p></o:p></span></p>
<p class="MsoNormal"><b><i>[David Spisla] Ok, so there is no chance to get that gfid in an initial lookup. Another problem seems to be that there is no loc parameter in lookup_cbk function. I have the buf->gfid and inode, but there is no loc with the path and
name oft he file. I I want to use syncop_getxattr but I have no loc as parameter. Can I get a loc struct with the gfid?<o:p></o:p></i></b></p>
<p class="MsoNormal"><b><i><o:p> </o:p></i></b></p>
<p class="MsoNormal"><b><i>David </i></b><o:p></o:p></p>
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_______________________________________________<br>
Gluster-devel mailing list<br>
<a href="mailto:Gluster-devel@gluster.org">Gluster-devel@gluster.org</a><br>
<a href="http://lists.gluster.org/mailman/listinfo/gluster-devel" target="_blank">http://lists.gluster.org/mailman/listinfo/gluster-devel</a><o:p></o:p></p>
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<p class="MsoNormal">-- <o:p></o:p></p>
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<p class="MsoNormal">Amar Tumballi (amarts)<o:p></o:p></p>
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