Date: Thu, 27 May 2021 16:52:21 +0000 From: bugzilla-noreply@freebsd.org To: bugs@FreeBSD.org Subject: [Bug 256205] lseek() with SEEK_HOLE some times wrongly reports holes on ZFS Message-ID: <bug-256205-227@https.bugs.freebsd.org/bugzilla/>
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=256205 Bug ID: 256205 Summary: lseek() with SEEK_HOLE some times wrongly reports holes on ZFS Product: Base System Version: 13.0-STABLE Hardware: Any OS: Any Status: New Severity: Affects Many People Priority: --- Component: kern Assignee: bugs@FreeBSD.org Reporter: fuz@fuz.su While experimenting with star on an arm64 FreeBSD 13.0-RELEASE system on ZFS, I noticed that star would some times spuriously consider files to be full of data holes when they do in fact not have any holes at all. A typical truss trace looks like this: 4677: openat(AT_FDCWD,"ved",O_RDONLY,00) = 3 (0x3) 4677: lseek(3,0x0,SEEK_HOLE) = 0 (0x0) 4677: write(2,"'ved' is sparse\n",16) = 16 (0x10) 4677: lseek(3,0x0,SEEK_HOLE) = 0 (0x0) 4677: lseek(3,0x0,SEEK_DATA) ERR#6 'Device not configured' 4677: lseek(3,0x37594,SEEK_HOLE) ERR#6 'Device not configured' 4677: lseek(3,0x0,SEEK_SET) = 0 (0x0) lseek(3, 0, SEEK_HOLE) returns 0, indicating that the file begins with a data hole. This is unlikely as the file ved is an ELF executable which always begins with \0177ELF. There are also spurious ENXIO returns from further lseek calls I do not understand. Copying the file before running star makes the problem go away: 4721: openat(AT_FDCWD,"ved",O_RDONLY,00) = 3 (0x3) 4721: lseek(3,0x0,SEEK_HOLE) = 226708 (0x37594) 4721: lseek(3,0x0,SEEK_SET) = 0 (0x0) It is difficult to reproduce this problem as it seems to only appear some times and on random executables. I believe this is a severe problem as wrong output from lseek(..., SEEK_HOLE, ...) may make “smart” copying and archiving programs generate corrupt copies/archives. This problem looks similar to #164445, but surely that bug has already been fixed long ago. -- You are receiving this mail because: You are the assignee for the bug.home | help
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