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| author |   Pavel Tikhomirov <ptikhomirov@virtuozzo.com> | 2024-11-19 17:39:01 +0800 |
|---|---|---|
| committer |   Jonathan Corbet <corbet@lwn.net> | 2024-11-22 10:42:37 -0700 |
| commit | 21e500138b6f3040423bb1959ac9ffe68d138733 (patch) | |
| tree | c96b2a6d3419c7ae83ddfe706eaaead493fb6364 | |
| parent | Documentation: kernel-doc: enumerate identifier *type*s (diff) | |
| download | wireguard-linux-21e500138b6f3040423bb1959ac9ffe68d138733.tar.xz wireguard-linux-21e500138b6f3040423bb1959ac9ffe68d138733.zip | |
docs: core-api/gfp_mask-from-fs-io: indicate that vmalloc supports GFP_NOFS/GFP_NOIO
After the commit 451769ebb7e79 ("mm/vmalloc: alloc GFP_NO{FS,IO} for
vmalloc") in v5.17 it is now safe to use GFP_NOFS/GFP_NOIO flags
in [k]vmalloc, let's reflect it in documentation.
Signed-off-by: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20241119093922.567138-1-ptikhomirov@virtuozzo.com
| -rw-r--r-- | Documentation/core-api/gfp_mask-from-fs-io.rst | 20 |
1 files changed, 11 insertions, 9 deletions
diff --git a/Documentation/core-api/gfp_mask-from-fs-io.rst b/Documentation/core-api/gfp_mask-from-fs-io.rst index e7c32a8de126..858b2fbcb36c 100644 --- a/Documentation/core-api/gfp_mask-from-fs-io.rst +++ b/Documentation/core-api/gfp_mask-from-fs-io.rst @@ -55,14 +55,16 @@ scope. What about __vmalloc(GFP_NOFS) ============================== -vmalloc doesn't support GFP_NOFS semantic because there are hardcoded -GFP_KERNEL allocations deep inside the allocator which are quite non-trivial -to fix up. That means that calling ``vmalloc`` with GFP_NOFS/GFP_NOIO is -almost always a bug. The good news is that the NOFS/NOIO semantic can be -achieved by the scope API. +Since v5.17, and specifically after the commit 451769ebb7e79 ("mm/vmalloc: +alloc GFP_NO{FS,IO} for vmalloc"), GFP_NOFS/GFP_NOIO are now supported in +``[k]vmalloc`` by implicitly using scope API. + +In earlier kernels ``vmalloc`` didn't support GFP_NOFS semantic because there +were hardcoded GFP_KERNEL allocations deep inside the allocator. That means +that calling ``vmalloc`` with GFP_NOFS/GFP_NOIO was almost always a bug. In the ideal world, upper layers should already mark dangerous contexts -and so no special care is required and vmalloc should be called without -any problems. Sometimes if the context is not really clear or there are -layering violations then the recommended way around that is to wrap ``vmalloc`` -by the scope API with a comment explaining the problem. +and so no special care is required and ``vmalloc`` should be called without any +problems. Sometimes if the context is not really clear or there are layering +violations then the recommended way around that (on pre-v5.17 kernels) is to +wrap ``vmalloc`` by the scope API with a comment explaining the problem. |