Hi Dongmin,<br><br>please find the inlined comments.<br><div class="gmail_quote">On Wed, Feb 17, 2010 at 4:05 PM, Dongmin Yu <span dir="ltr"><<a href="mailto:min@hostway.co.kr">min@hostway.co.kr</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<div link="blue" vlink="purple" lang="KO">
<div>
<p class="MsoNormal"><span lang="EN-US">Hello,</span></p>
<p class="MsoNormal"><span lang="EN-US"> </span></p>
<p class="MsoNormal"><span lang="EN-US">I’m trying to store additional metadata
like content-type and etc at extended attribute.</span></p>
<p class="MsoNormal"><span lang="EN-US"> </span></p>
<p class="MsoNormal"><span lang="EN-US">My client code are like</span></p>
<p class="MsoNormal"><span lang="EN-US"> </span></p>
<p class="MsoNormal"><span lang="EN-US">fd = glusterfs_open( path );</span></p>
<p class="MsoNormal"><span lang="EN-US">glusterfs_write( fd, data, data_length );</span></p>
<p class="MsoNormal"><span lang="EN-US">glusterfs_close( fd );
//------</span></p>
<p class="MsoNormal"><span lang="EN-US">glusterfs_setxattr( path, attr_name,
attr_value, value_length,0 );</span></p>
<p class="MsoNormal"><span lang="EN-US"> </span></p>
<p class="MsoNormal"><span lang="EN-US">My concern is that above client code runs
on multiple machines and multi-threaded.</span></p>
<p class="MsoNormal"><span lang="EN-US">In higher concurrency, client A could write
content, client B write content, client B write its attribute then client A
write its attribute.</span></p>
<p class="MsoNormal"><span lang="EN-US">So to speak, file content comes from client
B but attribute comes from client A.</span></p>
<p class="MsoNormal"><span lang="EN-US"> </span></p>
<p class="MsoNormal"><span lang="EN-US">If I use a lock server, I can guarantee
data integrity. But is there a simpler way to store extended attributes at an
atomic environment? </span></p></div></div></blockquote><div><br>locks should be used to ensure atomicity. There is no other simpler way which I can think of.<br> <br></div><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<div link="blue" vlink="purple" lang="KO"><div>
<p class="MsoNormal"><span lang="EN-US">I see another function, glusterfs_fsetxattr
which accepts open glusterfs_file descriptor. If I rewrite as following, can I
guarantee the integrity?</span></p>
<p class="MsoNormal"><span lang="EN-US"> </span></p>
<p class="MsoNormal"><span lang="EN-US">fd = glusterfs_open( path );</span></p>
<p class="MsoNormal"><span lang="EN-US">glusterfs_write( fd, data, data_length );</span></p>
<p class="MsoNormal"><span lang="EN-US">glusterfs_fsetxattr( fd, attr_name,
attr_value, value_length,0 );</span></p>
<p class="MsoNormal"><span lang="EN-US">glusterfs_close( fd ); </span></p>
<p class="MsoNormal"><span lang="EN-US"></span></p></div></div></blockquote><div><br>No.<br><br>One of the solutions I can think of is, <br><p class="MsoNormal"><span lang="EN-US">fd = glusterfs_open( path );</span></p><p class="MsoNormal">
glusterfs_fcntl (fd, F_SETLKW, flock); /* flock tries to hold write lock on whole file */</p><p class="MsoNormal"> /* please note usage of F_SETLKW, If you want to use F_SETLK you have to check for */<br>
<span lang="EN-US"></span></p><p class="MsoNormal"><span lang="EN-US"> /* return value and proceed with writing only after lock has been acquired */<br></span></p>
<p class="MsoNormal"><span lang="EN-US">glusterfs_write( fd, data, data_length );</span></p>
<p class="MsoNormal"><span lang="EN-US"></span></p>
<p class="MsoNormal"><span lang="EN-US">glusterfs_setxattr( path, attr_name,
attr_value, value_length,0 );</span></p><p class="MsoNormal">glusterfs_fcntl (fd, F_SETLKW, flock); /*flock tries to unlock */<span lang="EN-US"></span><br></p><p class="MsoNormal"><span lang="EN-US">glusterfs_close( fd );
//------</span></p><br></div><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"><div link="blue" vlink="purple" lang="KO"><div><p class="MsoNormal">
<span lang="EN-US"> </span></p>
<p class="MsoNormal"><span lang="EN-US"> </span></p>
<p class="MsoNormal"><span lang="EN-US">Thanks</span></p>
<p class="MsoNormal"><span lang="EN-US"> </span></p>
<p class="MsoNormal" style="text-align: left;" align="left"><b><span style="font-family: Gulim;" lang="EN-US">DongMin Yu</span></b><span style="font-size: 12pt; font-family: Gulim;" lang="EN-US"></span></p>
<p class="MsoNormal" style="text-align: left;" align="left"><span style="font-size: 12pt; font-family: Gulim;" lang="EN-US"> </span></p>
<p class="MsoNormal" style="text-align: left;" align="left"><span style="font-family: Gulim;" lang="EN-US">HOSTWAY IDC
Corp. / R&D Principal Researcher</span><span style="font-size: 12pt; font-family: Gulim;" lang="EN-US"></span></p>
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<br></blockquote></div><br><br clear="all">regards,<br>-- <br>Raghavendra G<br><br>