Feature #10463
use SEEK_DATA/SEEK_HOLE for FileStore fiemap() implementation
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Description
In an exchange on linux-fsdevel yesterday it became clear that even when
FIEMAP isn't buggy it's not a good interface to build a map of sparse
files. For example, XFS defrag or other future fs features may muck with
fiemap results. One wouldn't expect those things to change whether a file
extent is allocated or not allocated, but given what we've seen so far I
wouldn't bet on it.Instead, we should use lseek SEEK_DATA/SEEK_HOLE, which is a more natural
interface for what we need. This should simply be a matter of replacing
the fiemap() method implementation in FileStore.cc, I think.See this thread:
http://marc.info/?l=linux-fsdevel&m=142050204317588&w=2
The other half of this is we should confirm that xfstests.git has good
SEEK_HOLE/SEEK_DATA stress tests (that verify correct results on both
recently written, recently synced, and uncached files).
History
#1 Updated by Sage Weil about 9 years ago
- Target version changed from v0.94 to v0.93 - Last Hammer Sprint
#2 Updated by Neil Levine about 9 years ago
- Target version deleted (
v0.93 - Last Hammer Sprint)
#3 Updated by Haomai Wang about 9 years ago
- Assignee set to Haomai Wang
#4 Updated by Haomai Wang about 9 years ago
@sage
do we need to reserve or fallback to fiemap if SEEK_DATA not supported?
#5 Updated by Sage Weil almost 9 years ago
- Target version set to v0.95
#6 Updated by Sage Weil almost 9 years ago
- Status changed from New to Fix Under Review
#7 Updated by Sage Weil almost 9 years ago
- Status changed from Fix Under Review to Resolved