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Message-ID: <20171012134209.GE29293@quack2.suse.cz> Date: Thu, 12 Oct 2017 15:42:09 +0200 From: Jan Kara <jack@...e.cz> To: Dan Williams <dan.j.williams@...el.com> Cc: Jan Kara <jack@...e.cz>, linux-fsdevel <linux-fsdevel@...r.kernel.org>, linux-ext4 <linux-ext4@...r.kernel.org>, linux-xfs@...r.kernel.org, Christoph Hellwig <hch@...radead.org>, Ross Zwisler <ross.zwisler@...ux.intel.com>, Ted Tso <tytso@....edu>, "Darrick J. Wong" <darrick.wong@...cle.com> Subject: Re: [PATCH 17/19] ext4: Add support for MAP_SYNC flag On Wed 11-10-17 15:11:21, Dan Williams wrote: > On Wed, Oct 11, 2017 at 1:06 PM, Jan Kara <jack@...e.cz> wrote: > > Now when everything is prepared, add support in ext4 to accept MAP_SYNC > > as an mmap(2) flag. > > > > Signed-off-by: Jan Kara <jack@...e.cz> > > --- > > fs/ext4/file.c | 20 ++++++++++++++++++++ > > 1 file changed, 20 insertions(+) > > > > diff --git a/fs/ext4/file.c b/fs/ext4/file.c > > index 61a8788168f3..f013cda84b3d 100644 > > --- a/fs/ext4/file.c > > +++ b/fs/ext4/file.c > > @@ -364,6 +364,25 @@ static int ext4_file_mmap(struct file *file, struct vm_area_struct *vma) > > return 0; > > } > > > > +#define EXT4_SUPPORTED_MAP_FLAGS (LEGACY_MAP_MASK | MAP_SYNC) > > + > > +static int ext4_file_mmap_validate(struct file *file, > > + struct vm_area_struct *vma, > > + unsigned long map_flags) > > +{ > > + if (map_flags & ~EXT4_SUPPORTED_MAP_FLAGS) > > + return -EOPNOTSUPP; > > + > > + /* > > + * We don't support synchronous mappings for non-DAX files. At least > > + * until someone comes with a sensible use case. > > + */ > > + if (!IS_DAX(file_inode(file)) && (map_flags & MAP_SYNC)) > > + return -EOPNOTSUPP; > > Perhaps EPERM instead to differentiate the unsupported flags case? > There's precedent for mmap returning EPERM for reasons other than > incompatible PROT flags. Hum, I could make it EINVAL. EPERM looks just too bogus to me. Honza -- Jan Kara <jack@...e.com> SUSE Labs, CR
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