Messages in this thread | | | Date | Mon, 2 Oct 2023 10:51:36 +0100 | Subject | Re: [PATCH 03/21] fs/bdev: Add atomic write support info to statx | From | John Garry <> |
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On 01/10/2023 14:23, Bart Van Assche wrote: > On 9/29/23 15:49, Eric Biggers wrote: >> On Fri, Sep 29, 2023 at 10:27:08AM +0000, John Garry wrote: >>> diff --git a/include/uapi/linux/stat.h b/include/uapi/linux/stat.h >>> index 7cab2c65d3d7..c99d7cac2aa6 100644 >>> --- a/include/uapi/linux/stat.h >>> +++ b/include/uapi/linux/stat.h >>> @@ -127,7 +127,10 @@ struct statx { >>> __u32 stx_dio_mem_align; /* Memory buffer alignment for >>> direct I/O */ >>> __u32 stx_dio_offset_align; /* File offset alignment for >>> direct I/O */ >>> /* 0xa0 */ >>> - __u64 __spare3[12]; /* Spare space for future expansion */ >>> + __u32 stx_atomic_write_unit_max; >>> + __u32 stx_atomic_write_unit_min; >> >> Maybe min first and then max? That seems a bit more natural, and a >> lot of the >> code you've written handle them in that order.
ok, I think it's fine to reorder
>> >>> +#define STATX_ATTR_WRITE_ATOMIC 0x00400000 /* File supports >>> atomic write operations */ >> >> How would this differ from stx_atomic_write_unit_min != 0?
Yeah, I suppose that we can just not set this for the case of stx_atomic_write_unit_min == 0.
> > Is it even possible that stx_atomic_write_unit_min == 0? My understanding > is that all Linux filesystems rely on the assumption that writing a single > logical block either succeeds or does not happen, even if a power failure > occurs between writing and reading a logical block. >
Maybe they do rely on this, but is it particularly interesting?
BTW, I would not like to provide assurances that every storage media produced writes logical blocks atomically.
Thanks, John
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