This code would benefit from a little more explanation.
Also, I screwed up the previous patch and forgot to delete a line, so the
calculation here is off; fix it.
Signed-off-by: J. Bruce Fields <[email protected]>
---
fs/nfsd/nfs4state.c | 16 +++++++++++++++-
1 files changed, 15 insertions(+), 1 deletions(-)
On Mon, Jun 25, 2007 at 08:52:44PM -0700, Andrew Morton wrote:
>
> Please put yourself in the position of the reader who happens across this
> code and wonders why it is that way.
>
> They could of course go hunt it out of the git repo but I do think it's
> quite a bit more reader-friendly to explain the thinking in code comments.
>
Yup, sorry about that. Could you apply this?
--b.
diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index fbbbcab..1b2657f 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -3203,13 +3203,27 @@ get_nfs4_grace_period(void)
return max(user_lease_time, lease_time) * HZ;
}
+/*
+ * Since the lifetime of a delegation isn't limited to that of an open, a
+ * client may quite reasonably hang on to a delegation as long as it has
+ * the inode cached. This becomes an obvious problem the first time a
+ * client's inode cache approaches the size of the server's total memory.
+ *
+ * For now we avoid this problem by imposing a hard limit on the number
+ * of delegations, which varies according to the server's memory size.
+ */
static void
set_max_delegations(void)
{
struct sysinfo sys;
si_meminfo(&sys);
- sys.totalram *= sys.mem_unit;
+ /*
+ * Allow at most 4 delegations per megabyte of RAM. Quick
+ * estimates suggest that in the worst case (where every delegation
+ * is for a different inode), a delegation could take about 1.5K,
+ * giving a worst case usage of about 6% of memory.
+ */
sys.totalram >>= (18 - PAGE_SHIFT);
max_delegations = (unsigned int) sys.totalram;
}
--
1.5.2.58.g98ee
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