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    SubjectRe: [PATCH 2/6][TAKE7] fallocate() implementation in i386, x86_64 and powerpc
    On Fri, Jul 13, 2007 at 02:21:19PM +0100, Christoph Hellwig wrote:
    > On Fri, Jul 13, 2007 at 06:17:55PM +0530, Amit K. Arora wrote:
    > > /*
    > > + * sys_fallocate - preallocate blocks or free preallocated blocks
    > > + * @fd: the file descriptor
    > > + * @mode: mode specifies the behavior of allocation.
    > > + * @offset: The offset within file, from where allocation is being
    > > + * requested. It should not have a negative value.
    > > + * @len: The amount of space in bytes to be allocated, from the offset.
    > > + * This can not be zero or a negative value.
    >
    > kerneldoc comments are for in-kernel APIs which syscalls aren't. I'd say
    > just temove this comment, the manpage is a much better documentation anyway.

    Ok. I will remove this entire comment.

    > > + * <TBD> Generic fallocate to be added for file systems that do not
    > > + * support fallocate.
    >
    > Please remove the comment, adding a generic fallback in kernelspace is a
    > very dumb idea as we already discussed long time ago.
    >
    > > --- linux-2.6.22.orig/include/linux/fs.h
    > > +++ linux-2.6.22/include/linux/fs.h
    > > @@ -266,6 +266,21 @@ extern int dir_notify_enable;
    > > #define SYNC_FILE_RANGE_WRITE 2
    > > #define SYNC_FILE_RANGE_WAIT_AFTER 4
    > >
    > > +/*
    > > + * sys_fallocate modes
    > > + * Currently sys_fallocate supports two modes:
    > > + * FALLOC_ALLOCATE : This is the preallocate mode, using which an application
    > > + * may request reservation of space for a particular file.
    > > + * The file size will be changed if the allocation is
    > > + * beyond EOF.
    > > + * FALLOC_RESV_SPACE : This is same as the above mode, with only one difference
    > > + * that the file size will not be modified.
    > > + */
    > > +#define FALLOC_FL_KEEP_SIZE 0x01 /* default is extend/shrink size */
    > > +
    > > +#define FALLOC_ALLOCATE 0
    > > +#define FALLOC_RESV_SPACE FALLOC_FL_KEEP_SIZE
    >
    > Just remove FALLOC_ALLOCATE, 0 flags should be the default. I'm also
    > not sure there is any point in having two namespace now that we have a flags-
    > based ABI.

    Ok. Since we have only one flag (FALLOC_FL_KEEP_SIZE) and we do not want
    to declare the default mode (FALLOC_ALLOCATE), we can _just_ have this
    flag and remove the other mode too (FALLOC_RESV_SPACE).
    Is this what you are suggesting ?

    > Also please don't add this to fs.h. fs.h is a complete mess and the
    > falloc flags are a new user ABI. Add a linux/falloc.h instead which can
    > be added to headers-y so the ABI constant can be exported to userspace.

    Should we need a header file just to declare one flag - i.e.
    FALLOC_FL_KEEP_SIZE (since now there is no point of declaring the two
    modes) ? If "linux/fs.h" is not a good place, will "asm-generic/fcntl.h"
    be a sane place for this flag ?

    Thanks!
    --
    Regards,
    Amit Arora
    -
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