On 2025-01-15 10:26, Corinna Vinschen via Cygwin wrote:
On Jan 15 09:12, Brian Inglis via Cygwin wrote:
On 2025-01-14 03:13, Roland Mainz via Cygwin wrote:
On Tue, Jan 14, 2025 at 7:19 AM Brian Inglis via Cygwin
<cygwin@cygwin.com> wrote:
On 2025-01-13 13:10, Roland Mainz via Cygwin wrote:
I just hit an endless loop with /usr/bin/cp from "coreutils" version
9.5-1 copying a larger *.pdb file (it seems that only this specific
file is affected...) from Visual Studio 19.
[...]
I think I found the problem:
The *.pdb file uses NTFS compression:
---- snip ----
/bin/winfsinfo filebasicinfo "$(cygpath -w
$PWD/../build.vc19/x64/Debug/nfs41_driver.pdb)"
(
filename='C:\cygwin64\home\roland_mainz\work\msnfs41_uidmapping\ms-nfs41-client-kofemannvacation\build.vc19\x64\Debug\nfs41_driver.pdb'
CreationTime=133812707624654816
LastAccessTime=133813220892976366
LastWriteTime=133812707639811081
ChangeTime=133812707639811081
typeset -a FileAttributes=(
FILE_ATTRIBUTE_ARCHIVE
FILE_ATTRIBUTE_COMPRESSED
)
)
---- snip ----
If I remove the "FILE_ATTRIBUTE_COMPRESSED" flag /bin/cp works without problems.
I think the issues here are:
1. Coreutils 9.5-1 /bin/cp erroneously assumes that a file is sparse
if the number of blocks is smaller than $((filesize / fs_blocksize)) -
but in this case the file is NOT sparse, just compressed.
2. The loop to copy a sparse file is faulty because there are no holes
in that file. That itself is IMHO already a bad idea to have a
separate codepath for sparse files, just the normal codepath should
use SEEK_HOLE and just skip those in the destination
A possible issue is that Cygwin assumes sparse files on SSD
No, that's not the problem, because SPARSE handling requires that
the FILE_ATTRIBUTE_SPARSE_FILE flag of the file is actually set.
For instance, see lseek w/ SEEK_DATA/SEEK_HOLE, which handles
non-sparse files as documented by the Linux man page
https://man7.org/linux/man-pages/man2/lseek.2.html:
if (!has_attribute (FILE_ATTRIBUTE_SPARSE_FILE))
{
/* Default behaviour if sparse files are not supported:
SEEK_DATA: seek to offset
SEEK_HOLE: seek to EOF */
fpi.CurrentByteOffset.QuadPart = (whence == SEEK_DATA)
? offset
: fsi.EndOfFile.QuadPart;
break;
}
so we need
fhandler/disk_file:fstat_helper to allow cp to handle compressed files
normally.
Say again? What exactly are you expecting from stat()? Fibbing about
the number of blocks taken by a FS-compressed file?
Just a suggestion to work around the issue transparently?
For the time being, it seems the assumption that #blocks * blocksize <
filesize is not really correct.
Actually cp(1) should test if lseek(SEEK_HOLE) returns EOF. If so,
the file isn't sparse.
On Cygwin it could also check with
(ioctl (fd, FS_IOC_GETFLAGS, &flags) & FS_SPARSE_FL) != 0
that the file is sparse, but the lseek test is target-independent.
On Cygwin and Linux you could also test with
(ioctl (fd, FS_IOC_GETFLAGS, &flags) & FS_COMPR_FL) != 0
that the file is compressed, but there's a problem so far. The
Linux flag is called FS_COMPR_FL but the Cygwin flag is called
FS_COMPRESSED_FL. THis flag is only supported on btrfs and I'm
not sure it already existed when I added FS_IOC_GETFLAGS...
Anyway, I'll change FS_COMPR_FL to FS_COMPRESSED_FL and make
FS_COMPRESSED_FL an alias for backward compat...
Thanks - I'll submit a bug report and ask what approach they would prefer?
--
Take care. Thanks, Brian Inglis Calgary, Alberta, Canada
La perfection est atteinte Perfection is achieved
non pas lorsqu'il n'y a plus rien à ajouter not when there is no more to add
mais lorsqu'il n'y a plus rien à retrancher but when there is no more to cut
-- Antoine de Saint-Exupéry
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