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Tue, 27 Feb 2024 18:14:19 -0800 (PST) Date: Tue, 27 Feb 2024 18:14:17 -0800 In-Reply-To: <20240227232100.478238-18-pbonzini@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20240227232100.478238-1-pbonzini@redhat.com> <20240227232100.478238-18-pbonzini@redhat.com> Message-ID: Subject: Re: [PATCH 17/21] filemap: add FGP_CREAT_ONLY From: Sean Christopherson To: Paolo Bonzini Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, michael.roth@amd.com, isaku.yamahata@intel.com, thomas.lendacky@amd.com Content-Type: text/plain; charset="us-ascii" On Tue, Feb 27, 2024, Paolo Bonzini wrote: This needs a changelog, and also needs to be Cc'd to someone(s) that can give it a thumbs up. > Signed-off-by: Paolo Bonzini > --- > include/linux/pagemap.h | 2 ++ > mm/filemap.c | 4 ++++ > 2 files changed, 6 insertions(+) > > diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h > index 2df35e65557d..e8ac0b32f84d 100644 > --- a/include/linux/pagemap.h > +++ b/include/linux/pagemap.h > @@ -586,6 +586,7 @@ pgoff_t page_cache_prev_miss(struct address_space *mapping, > * * %FGP_CREAT - If no folio is present then a new folio is allocated, > * added to the page cache and the VM's LRU list. The folio is > * returned locked. > + * * %FGP_CREAT_ONLY - Fail if a folio is not present > * * %FGP_FOR_MMAP - The caller wants to do its own locking dance if the > * folio is already in cache. If the folio was allocated, unlock it > * before returning so the caller can do the same dance. > @@ -606,6 +607,7 @@ typedef unsigned int __bitwise fgf_t; > #define FGP_NOWAIT ((__force fgf_t)0x00000020) > #define FGP_FOR_MMAP ((__force fgf_t)0x00000040) > #define FGP_STABLE ((__force fgf_t)0x00000080) > +#define FGP_CREAT_ONLY ((__force fgf_t)0x00000100) > #define FGF_GET_ORDER(fgf) (((__force unsigned)fgf) >> 26) /* top 6 bits */ > > #define FGP_WRITEBEGIN (FGP_LOCK | FGP_WRITE | FGP_CREAT | FGP_STABLE) > diff --git a/mm/filemap.c b/mm/filemap.c > index 750e779c23db..d5107bd0cd09 100644 > --- a/mm/filemap.c > +++ b/mm/filemap.c > @@ -1854,6 +1854,10 @@ struct folio *__filemap_get_folio(struct address_space *mapping, pgoff_t index, > folio = NULL; > if (!folio) > goto no_page; > + if (fgp_flags & FGP_CREAT_ONLY) { > + folio_put(folio); > + return ERR_PTR(-EEXIST); > + } > > if (fgp_flags & FGP_LOCK) { > if (fgp_flags & FGP_NOWAIT) { > -- > 2.39.0 > >