[Bug-tar] seek_hole proposal

[Pavel Raiskup]

Hello all,

I am trying to prepare patch which would reuse lseek's
SEEK_HOLE/SEEK_DATA, the [v1] is attached.  Some info:

Note that after discussion [1] I still think that existing ST_IS_SPARSE
macro is better for file-sparseness detection than using SEEK_HOLE (not
worth having additional syscalls open~>seek~>close).

I have played with similar idea; changing "fstatat() ~> open()" sequence
to "open() ~> fstat() (and close eventually if file is not dumpable..)".
this case, we would need only two calls of lseek().  I have such patch but
I reverted it locally due to unnecessary complexity (I can share if you
were interested, that could be useful for some more precise sparseness
detection; concretely for sparse files of size < 512B).

Note that I don't know what the scan_parse() callback should be used for
so I didn't used in new function sparse_scan_file_seek.  Some help would
be needed.

[1] http://www.mail-archive.com/address@hidden/msg04199.html

Thanks for any comment,

Pavel

PS: Use --ignore-space-change due to some indentation changes

0001-tar-use-SEEK_HOLE-for-hole-detection.patch
Description: Text Data

testsuite.log.gz
Description: application/gzip