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authorPaul Menzel <pmenzel@molgen.mpg.de>2019-07-03 11:28:15 (GMT)
committerJ. Bruce Fields <bfields@redhat.com>2019-07-03 21:51:31 (GMT)
commit3b2d4dcf71c4a91b420f835e52ddea8192300a3b (patch)
tree3d184fbf8a5c7482910ec46ebb2b102a4c0ae3d5 /fs
parent1e091c3bbf51d34d5d96337a59ce5ab2ac3ba2cc (diff)
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nfsd: Fix overflow causing non-working mounts on 1 TB machines
Since commit 10a68cdf10 (nfsd: fix performance-limiting session calculation) (Linux 5.1-rc1 and 4.19.31), shares from NFS servers with 1 TB of memory cannot be mounted anymore. The mount just hangs on the client. The gist of commit 10a68cdf10 is the change below. -avail = clamp_t(int, avail, slotsize, avail/3); +avail = clamp_t(int, avail, slotsize, total_avail/3); Here are the macros. #define min_t(type, x, y) __careful_cmp((type)(x), (type)(y), <) #define clamp_t(type, val, lo, hi) min_t(type, max_t(type, val, lo), hi) `total_avail` is 8,434,659,328 on the 1 TB machine. `clamp_t()` casts the values to `int`, which for 32-bit integers can only hold values −2,147,483,648 (−2^31) through 2,147,483,647 (2^31 − 1). `avail` (in the function signature) is just 65536, so that no overflow was happening. Before the commit the assignment would result in 21845, and `num = 4`. When using `total_avail`, it is causing the assignment to be 18446744072226137429 (printed as %lu), and `num` is then 4164608182. My next guess is, that `nfsd_drc_mem_used` is then exceeded, and the server thinks there is no memory available any more for this client. Updating the arguments of `clamp_t()` and `min_t()` to `unsigned long` fixes the issue. Now, `avail = 65536` (before commit 10a68cdf10 `avail = 21845`), but `num = 4` remains the same. Fixes: c54f24e338ed (nfsd: fix performance-limiting session calculation) Cc: stable@vger.kernel.org Signed-off-by: Paul Menzel <pmenzel@molgen.mpg.de> Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Diffstat (limited to 'fs')
-rw-r--r--fs/nfsd/nfs4state.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 618e660..1a0cdeb 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -1563,7 +1563,7 @@ static u32 nfsd4_get_drc_mem(struct nfsd4_channel_attrs *ca)
* Never use more than a third of the remaining memory,
* unless it's the only way to give this client a slot:
*/
- avail = clamp_t(int, avail, slotsize, total_avail/3);
+ avail = clamp_t(unsigned long, avail, slotsize, total_avail/3);
num = min_t(int, num, avail / slotsize);
nfsd_drc_mem_used += num * slotsize;
spin_unlock(&nfsd_drc_lock);