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2017-07-14DMA-ISA-LPC.txt: standardize document formatMauro Carvalho Chehab1-35/+36
Each text file under Documentation follows a different format. Some doesn't even have titles! Change its representation to follow the adopted standard, using ReST markups for it to be parseable by Sphinx: - use proper markups for titles; - use :Author: for authorship; - identify the literal blocks. Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2017-07-13mm, tree wide: replace __GFP_REPEAT by __GFP_RETRY_MAYFAIL with more useful ↵Michal Hocko1-1/+1
semantic __GFP_REPEAT was designed to allow retry-but-eventually-fail semantic to the page allocator. This has been true but only for allocations requests larger than PAGE_ALLOC_COSTLY_ORDER. It has been always ignored for smaller sizes. This is a bit unfortunate because there is no way to express the same semantic for those requests and they are considered too important to fail so they might end up looping in the page allocator for ever, similarly to GFP_NOFAIL requests. Now that the whole tree has been cleaned up and accidental or misled usage of __GFP_REPEAT flag has been removed for !costly requests we can give the original flag a better name and more importantly a more useful semantic. Let's rename it to __GFP_RETRY_MAYFAIL which tells the user that the allocator would try really hard but there is no promise of a success. This will work independent of the order and overrides the default allocator behavior. Page allocator users have several levels of guarantee vs. cost options (take GFP_KERNEL as an example) - GFP_KERNEL & ~__GFP_RECLAIM - optimistic allocation without _any_ attempt to free memory at all. The most light weight mode which even doesn't kick the background reclaim. Should be used carefully because it might deplete the memory and the next user might hit the more aggressive reclaim - GFP_KERNEL & ~__GFP_DIRECT_RECLAIM (or GFP_NOWAIT)- optimistic allocation without any attempt to free memory from the current context but can wake kswapd to reclaim memory if the zone is below the low watermark. Can be used from either atomic contexts or when the request is a performance optimization and there is another fallback for a slow path. - (GFP_KERNEL|__GFP_HIGH) & ~__GFP_DIRECT_RECLAIM (aka GFP_ATOMIC) - non sleeping allocation with an expensive fallback so it can access some portion of memory reserves. Usually used from interrupt/bh context with an expensive slow path fallback. - GFP_KERNEL - both background and direct reclaim are allowed and the _default_ page allocator behavior is used. That means that !costly allocation requests are basically nofail but there is no guarantee of that behavior so failures have to be checked properly by callers (e.g. OOM killer victim is allowed to fail currently). - GFP_KERNEL | __GFP_NORETRY - overrides the default allocator behavior and all allocation requests fail early rather than cause disruptive reclaim (one round of reclaim in this implementation). The OOM killer is not invoked. - GFP_KERNEL | __GFP_RETRY_MAYFAIL - overrides the default allocator behavior and all allocation requests try really hard. The request will fail if the reclaim cannot make any progress. The OOM killer won't be triggered. - GFP_KERNEL | __GFP_NOFAIL - overrides the default allocator behavior and all allocation requests will loop endlessly until they succeed. This might be really dangerous especially for larger orders. Existing users of __GFP_REPEAT are changed to __GFP_RETRY_MAYFAIL because they already had their semantic. No new users are added. __alloc_pages_slowpath is changed to bail out for __GFP_RETRY_MAYFAIL if there is no progress and we have already passed the OOM point. This means that all the reclaim opportunities have been exhausted except the most disruptive one (the OOM killer) and a user defined fallback behavior is more sensible than keep retrying in the page allocator. [akpm@linux-foundation.org: fix arch/sparc/kernel/mdesc.c] [mhocko@suse.com: semantic fix] Link: http://lkml.kernel.org/r/20170626123847.GM11534@dhcp22.suse.cz [mhocko@kernel.org: address other thing spotted by Vlastimil] Link: http://lkml.kernel.org/r/20170626124233.GN11534@dhcp22.suse.cz Link: http://lkml.kernel.org/r/20170623085345.11304-3-mhocko@kernel.org Signed-off-by: Michal Hocko <mhocko@suse.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> Cc: Alex Belits <alex.belits@cavium.com> Cc: Chris Wilson <chris@chris-wilson.co.uk> Cc: Christoph Hellwig <hch@infradead.org> Cc: Darrick J. Wong <darrick.wong@oracle.com> Cc: David Daney <david.daney@cavium.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Mel Gorman <mgorman@suse.de> Cc: NeilBrown <neilb@suse.com> Cc: Ralf Baechle <ralf@linux-mips.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-02-13Documentation: DMA-ISA-LPC.txtNathan Howard1-1/+1
Fixed spelling issue. Signed-off-by: Nathan Howard <adanhawthorn@gmail.com> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2014-05-21DMA-API: Clarify physical/bus address distinctionBjorn Helgaas1-2/+2
The DMA-API documentation sometimes refers to "physical addresses" when it really means "bus addresses." Sometimes these are identical, but they may be different if the bridge leading to the bus performs address translation. Update the documentation to use "bus address" when appropriate. Also, consistently capitalize "DMA", use parens with function names, use dev_printk() in examples, and reword a few sections for clarity. No functional change; documentation changes only. Signed-off-by: Bjorn Helgaas <bhelgaas@google.com> Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Acked-by: Arnd Bergmann <arnd@arndb.de> Acked-by: James Bottomley <jbottomley@Parallels.com> Acked-by: Randy Dunlap <rdunlap@infradead.org>
2006-11-30Fix typos in /Documentation : 'T''Matt LaPlante1-1/+1
This patch fixes typos in various Documentation txts. The patch addresses some +words starting with the letter 'T'. Signed-off-by: Matt LaPlante <kernel1@cyberdogtech.com> Acked-by: Randy Dunlap <rdunlap@xenotime.net> Signed-off-by: Adrian Bunk <bunk@stusta.de>
2005-09-10[PATCH] ISA DMA API documentationPierre Ossman1-0/+151
Documentation for how the ISA DMA controller is handled in the kernel. Signed-off-by: Pierre Ossman <drzeus@drzeus.cx> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>