Messages in this thread | | | From | Greg Freemyer <> | Date | Tue, 16 Nov 2010 12:47:20 -0800 | Subject | Re: [PATCH 4/6] Ext4: fail if we try to use hole punch |
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On Tue, Nov 16, 2010 at 8:05 AM, Josef Bacik <josef@redhat.com> wrote: > On Tue, Nov 16, 2010 at 03:07:29PM +0200, Avi Kivity wrote: >> On 11/16/2010 02:50 PM, Josef Bacik wrote: >>> On Tue, Nov 16, 2010 at 02:25:35PM +0200, Avi Kivity wrote: >>> > On 11/15/2010 07:05 PM, Josef Bacik wrote: >>> >> Ext4 doesn't have the ability to punch holes yet, so make sure we return >>> >> EOPNOTSUPP if we try to use hole punching through fallocate. This support can >>> >> be added later. Thanks, >>> >> >>> > >>> > Instead of teaching filesystems to fail if they don't support the >>> > capability, why don't supporting filesystems say so, allowing the fail >>> > code to be in common code? >>> > >>> >>> There is no simple way to test if a filesystem supports hole punching or not so >>> the check has to be done per fs. Thanks, >> >> Could put a flag word in superblock_operations. Filesystems which >> support punching (or other features) can enable it there. >> >> Or even have its own callback. >> > > Sure but then you have to do the same thing for every other flag you add to > fallocate and then you have this huge mess of random flags just so you don't > call into the filesystem. This way is a lesser of two evils I think. Thanks, > > Josef
I'm not a true kernel hacker, so my opinion is not critical but I find it hard to read / expand as
> + /* We only support the FALLOC_FL_KEEP_SIZE mode */ > + if (mode && (mode != FALLOC_FL_KEEP_SIZE)) > + return -EOPNOTSUPP;
How about:
#define EXT4_FALLOC_MODES_SUPPORTED (FALLOC_FL_KEEP_SIZE)
if (modes & ~EXT4_FALLOC_MODES_SUPPORTED) return -EOPNOTSUPP;
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