Author: glebius
Date: Mon Mar 16 14:24:47 2015
New Revision: 280136
URL: https://svnweb.freebsd.org/changeset/base/280136
Log:
Provide a comment explaining r279688.
Suggested by: alc
Modified:
head/sys/vm/vnode_pager.c
Modified: head/sys/vm/vnode_pager.c
==============================================================================
--- head/sys/vm/vnode_pager.c Mon Mar 16 14:12:41 2015 (r280135)
+++ head/sys/vm/vnode_pager.c Mon Mar 16 14:24:47 2015 (r280136)
@@ -772,6 +772,14 @@ vnode_pager_generic_getpages(struct vnod
bsize = vp->v_mount->mnt_stat.f_iosize;
foff = IDX_TO_OFF(m[reqpage]->pindex);
+ /*
+ * Synchronous and asynchronous paging operations use different
+ * free pbuf counters. This is done to avoid asynchronous requests
+ * to consume all pbufs.
+ * Allocate the pbuf at the very beginning of the function, so that
+ * if we are low on certain kind of pbufs don't even proceed to BMAP,
+ * but sleep.
+ */
freecnt = iodone != NULL ?
&vnode_async_pbuf_freecnt : &vnode_pbuf_freecnt;
bp = getpbuf(freecnt);
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