[Bug 12305] New: --fallocate and --sparse works wrong
samba-bugs at samba.org
samba-bugs at samba.org
Sat Oct 1 13:58:26 UTC 2016
https://bugzilla.samba.org/show_bug.cgi?id=12305
Bug ID: 12305
Summary: --fallocate and --sparse works wrong
Product: rsync
Version: 3.1.1
Hardware: All
OS: Linux
Status: NEW
Severity: normal
Priority: P5
Component: core
Assignee: wayned at samba.org
Reporter: socketpair at gmail.com
QA Contact: rsync-qa at samba.org
1.If I specify --fallocate without --sparse:
Sparse areas of SRC become fallocated on DST. This is not what I expect.
2. If I specify --sparse without --fallocate:
Fallocated areas of SRC become sparse areas on DST, meaning that very important
"attribute" is copied.
3. If I specify both --sparse and --fallocate:
Fallocate will win. see 1.
4. If I specify none of these flags:
sparse/preallocate information will be lost on DST.
This all is very sad.
So, during synchronisation, rsync should send type of the each area, which
should be on of:
1) containig user-data
2) sparse (contains zeroes)
3) preallocated (contain zeroes)
And receiver should apply that information on target file.
Note, that plain file may have preallocated space AFTER END OF FILE -- it is
not a bug, and should be transferred.
Also, receiver side may not handle all that features, so it should be
controllable what rsync receiver will do if making sparse or preallocated area
fails with EOPNOTSUPP or so.
Detecting holes and preallocated areas may give wrong information since some
FSes fake answer. So it should be controllable
see:
man 2 fallocate for possible modern operations.
man 2 lseek: detecting that areas (SEEK_HOLE/SEEK_DATA)
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