-
由 Dave Chinner 提交于
Both direct IO and DAX pass an offset and count into get_blocks that will overflow a s64 variable when an IO goes into the last supported block in a file (i.e. at offset 2^63 - 1FSB bytes). This can be seen from the tracing: xfs_get_blocks_alloc: [...] offset 0x7ffffffffffff000 count 4096 xfs_gbmap_direct: [...] offset 0x7ffffffffffff000 count 4096 xfs_gbmap_direct_none:[...] offset 0x7ffffffffffff000 count 4096 0x7ffffffffffff000 + 4096 = 0x8000000000000000, and hence that overflows the s64 offset and we fail to detect the need for a filesize update and an ioend is not allocated. This is *mostly* avoided for direct IO because such extending IOs occur with full block allocation, and so the "IS_UNWRITTEN()" check still evaluates as true and we get an ioend that way. However, doing single sector extending IOs to this last block will expose the fact that file size updates will not occur after the first allocating direct IO as the overflow will then be exposed. There is one further complexity: the DAX page fault path also exposes the same issue in block allocation. However, page faults cannot extend the file size, so in this case we want to allocate the block but do not want to allocate an ioend to enable file size update at IO completion. Hence we now need to distinguish between the direct IO patch allocation and dax fault path allocation to avoid leaking ioend structures. Signed-off-by: NDave Chinner <dchinner@redhat.com> Reviewed-by: NBrian Foster <bfoster@redhat.com> Signed-off-by: NDave Chinner <david@fromorbit.com>
3e12dbbd