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On Dec 22, 2020, at 13:25, Sudheendra Sampath <<a href="mailto:sudheendra.sampath@gmail.com" class="">sudheendra.sampath@gmail.com</a>> wrote:<br class="">
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<div dir="ltr" class="">Hi,
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<div class="">I was trying to understand more about LDLM, specifically Lock Value Block (LVB's) and stumbled upon the following code block :</div>
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<div class="">static int mdc_resource_inode_free(struct ldlm_resource *res)<br class="">
{<br class="">
if (res->lr_lvb_inode)<br class="">
res->lr_lvb_inode = NULL;<br class="">
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return 0;<br class="">
}<br class="">
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<div class="">Shouldn't the pointer (lr_lvb_inode) be freed before assigning it to NULL ? </div>
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<div class="">Just curious to know.</div>
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<div>The "lr_lvb_inode" pointer is a pointer to the VFS inode that is referencing a lock/resource:</div>
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<div>int mdc_set_lock_data(struct obd_export *exp, const struct lustre_handle *lockh,<br class="">
void *data, __u64 *bits)<br class="">
{</div>
<div> struct inode *new_inode = data;<br class="">
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<div> lock->l_resource->lr_lvb_inode = new_inode;</div>
<div>}</div>
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<div>The inode is allocated/freed separately by the VFS. The lr_lvb_inode pointer is used to quickly find the VFS inode from a DLM resource, but does not take a reference on the inode itself. Otherwise, the inode would always have an elevated reference count
and would never be freed by the VFS.</div>
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<div>Cheers, Andreas</div>
<div>--</div>
<div>Andreas Dilger</div>
<div>Principal Lustre Architect</div>
<div>Whamcloud</div>
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