Eric Sandeen wrote:
> Eric Sandeen wrote:
>> This should fix the longstanding issues with xfs and old ABI
>> arm boxes, which lead to various asserts and xfs shutdowns,
>> and for which an (incorrect) patch has been floating around
>> for years. (Said patch made ARM internally consistent, but
>> altered the normal xfs on-disk format such that it looked
>> corrupted on other architectures):
>> http://lists.arm.linux.org.uk/lurker/message/20040311.002034.5ecf21a2.html
>
> ping again...
ping #3...
> There is still the cache flushing issue, I guess, but I think the
> on-disk alignment is still worth fixing.
>
> Oh, I'm sorry Jeff - I meant "fixing." :)
>
> Thanks,
> -Eric
>
>> Old ABI ARM has interesting packing & padding; for example
>> on ARM old abi:
>>
>> struct xfs_dir2_sf_entry {
>> __uint8_t namelen; /* 0 1 */
>>
>> /* XXX 3 bytes hole, try to pack */
>>
>> xfs_dir2_sf_off_t offset; /* 4 4 */
>> __uint8_t name[1]; /* 8 1 */
>>
>> /* XXX 3 bytes hole, try to pack */
>>
>> xfs_dir2_inou_t inumber; /* 12 8 */
>>
>> /* size: 20, cachelines: 1 */
>> /* sum members: 14, holes: 2, sum holes: 6 */
>> /* last cacheline: 20 bytes */
>> };
>>
>> but on x86:
>>
>> struct xfs_dir2_sf_entry {
>> __uint8_t namelen; /* 0 1 */
>> xfs_dir2_sf_off_t offset; /* 1 2 */
>> __uint8_t name[1]; /* 3 1 */
>> xfs_dir2_inou_t inumber; /* 4 8 */
>>
>> /* size: 12, cachelines: 1 */
>> /* last cacheline: 12 bytes */
>> };
>>
>> ... this sort of discrepancy leads to problems.
>>
>> I've verified this patch by comparing the on-disk structure
>> layouts using pahole from the dwarves package, as well as
>> running through a bit of xfsqa under qemu-arm, modified so
>> that the check/repair phase after each test actually executes
>> check/repair from the x86 host, on the filesystem populated
>> by the arm emulator. Thus far it all looks good.
>>
>> There are 2 other structures with extra padding at the end,
>> but they don't seem to cause trouble. I suppose they could
>> be packed as well: xfs_dir2_data_unused_t and xfs_dir2_sf_t.
>>
>> Note that userspace needs a similar treatment, and any
>> filesystems which were running with the previous rogue
>> "fix" will now see corruption (either in the kernel, or
>> during xfs_repair) with this fix properly in place; it
>> may be worth teaching xfs_repair to identify and fix that
>> specific issue.
>>
>> Signed-off-by: Eric Sandeen <sandeen@xxxxxxxxxxx>
>>
>> ---
>>
>> Index: linux-2.6.24/fs/xfs/linux-2.6/xfs_linux.h
>> ===================================================================
>> --- linux-2.6.24.orig/fs/xfs/linux-2.6/xfs_linux.h
>> +++ linux-2.6.24/fs/xfs/linux-2.6/xfs_linux.h
>> @@ -300,4 +300,11 @@ static inline __uint64_t howmany_64(__ui
>> return x;
>> }
>>
>> +/* ARM old ABI has some weird alignment/padding */
>> +#if defined(__arm__) && !defined(__ARM_EABI__)
>> +#define __arch_pack __attribute__((packed))
>> +#else
>> +#define __arch_pack
>> +#endif
>> +
>> #endif /* __XFS_LINUX__ */
>> Index: linux-2.6.24/fs/xfs/xfs_dir2_sf.h
>> ===================================================================
>> --- linux-2.6.24.orig/fs/xfs/xfs_dir2_sf.h
>> +++ linux-2.6.24/fs/xfs/xfs_dir2_sf.h
>> @@ -62,7 +62,7 @@ typedef union {
>> * Normalized offset (in a data block) of the entry, really
>> xfs_dir2_data_off_t.
>> * Only need 16 bits, this is the byte offset into the single block form.
>> */
>> -typedef struct { __uint8_t i[2]; } xfs_dir2_sf_off_t;
>> +typedef struct { __uint8_t i[2]; } __arch_pack xfs_dir2_sf_off_t;
>>
>> /*
>> * The parent directory has a dedicated field, and the self-pointer must
>> @@ -76,14 +76,14 @@ typedef struct xfs_dir2_sf_hdr {
>> __uint8_t count; /* count of entries */
>> __uint8_t i8count; /* count of 8-byte inode #s */
>> xfs_dir2_inou_t parent; /* parent dir inode number */
>> -} xfs_dir2_sf_hdr_t;
>> +} __arch_pack xfs_dir2_sf_hdr_t;
>>
>> typedef struct xfs_dir2_sf_entry {
>> __uint8_t namelen; /* actual name length */
>> xfs_dir2_sf_off_t offset; /* saved offset */
>> __uint8_t name[1]; /* name, variable size */
>> xfs_dir2_inou_t inumber; /* inode number, var. offset */
>> -} xfs_dir2_sf_entry_t;
>> +} __arch_pack xfs_dir2_sf_entry_t;
>>
>> typedef struct xfs_dir2_sf {
>> xfs_dir2_sf_hdr_t hdr; /* shortform header */
>>
>>
>>
>
>
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