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authorFabio M. De Francesco <fmdefrancesco@gmail.com>2022-10-12 13:23:23 +0200
committerMiklos Szeredi <mszeredi@redhat.com>2022-11-23 09:10:49 +0100
commita1db2f7edef095a385d477ab81e780694d63eebd (patch)
treed157407a1f4e44aeb5bc26262ff5cc123b8d9838 /fs/fuse
parent44361e8cf9ddb23f17bdcc40ca944abf32e83e79 (diff)
downloadlwn-a1db2f7edef095a385d477ab81e780694d63eebd.tar.gz
lwn-a1db2f7edef095a385d477ab81e780694d63eebd.zip
fs/fuse: Replace kmap() with kmap_local_page()
The use of kmap() is being deprecated in favor of kmap_local_page(). There are two main problems with kmap(): (1) It comes with an overhead as the mapping space is restricted and protected by a global lock for synchronization and (2) it also requires global TLB invalidation when the kmap’s pool wraps and it might block when the mapping space is fully utilized until a slot becomes available. With kmap_local_page() the mappings are per thread, CPU local, can take page faults, and can be called from any context (including interrupts). It is faster than kmap() in kernels with HIGHMEM enabled. Furthermore, the tasks can be preempted and, when they are scheduled to run again, the kernel virtual addresses are restored and still valid. Therefore, replace kmap() with kmap_local_page() in fuse_readdir_cached(), it being the only call site of kmap() currently left in fs/fuse. Cc: "Venkataramanan, Anirudh" <anirudh.venkataramanan@intel.com> Suggested-by: Ira Weiny <ira.weiny@intel.com> Signed-off-by: Fabio M. De Francesco <fmdefrancesco@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Diffstat (limited to 'fs/fuse')
-rw-r--r--fs/fuse/readdir.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/fs/fuse/readdir.c b/fs/fuse/readdir.c
index e8deaacf1832..dc603479b30e 100644
--- a/fs/fuse/readdir.c
+++ b/fs/fuse/readdir.c
@@ -547,9 +547,9 @@ retry_locked:
* Contents of the page are now protected against changing by holding
* the page lock.
*/
- addr = kmap(page);
+ addr = kmap_local_page(page);
res = fuse_parse_cache(ff, addr, size, ctx);
- kunmap(page);
+ kunmap_local(addr);
unlock_page(page);
put_page(page);