New: ext4 in data=journal mode does not support delayed allocation
https://bugzilla.kernel.org/show_bug.cgi?id=16223
Summary: ext4 in data=journal mode does not support delayed
allocation
Product: File System
Version: 2.5
Kernel Version: 2.6.34
Platform: All
OS/Version: Linux
Tree: Mainline
Status: NEW
Severity: normal
Priority: P1
Component: ext4
AssignedTo: [email protected]
ReportedBy: [email protected]
Regression: No
Perhaps you could argue that someone using data=journal mode doesn't care about write performance, but that would not necessarily be the case. It would be really nice if I could use ext4 with data journaling AND get delayed allocation. I'm just mentioning this because I'm probably not the only one out there with this feeling. In fact, I know I'm not because I've seen the question asked in forums.
I suspect it might be nontrivial to modify the journaling system so that you can write data to the journal that has not yet been allocated a location on the disk, but it seems to me that's basically what you'd have to do. (Otherwise it wouldn't be DELAYED allocation, and we need data to hit the journal before it hits the fs proper.) Data would be written to the journal, then when it's going to be committed to the fs, it would be allocated (and that fact added to the journal?). If the system goes down, and a journal replay is required, then the data would be allocated space at that time. One thing to be concerned about is having an allocation happen, the data not written to where it's allocated, and the allocation not logged in the journal--on replay, you might allocate yet more space for the data, and you'd need some means to recover the first allocation that's now bogus.
Thanks.
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[Bug 16223] ext4 in data=journal mode does not support delayed allocation
https://bugzilla.kernel.org/show_bug.cgi?id=16223
Alan <[email protected]> changed:
What |Removed |Added
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Status|NEW |RESOLVED
CC| |[email protected]
Resolution| |OBSOLETESignature · 3 lines
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[Bug 16223] ext4 in data=journal mode does not support delayed allocation
In reply to [email protected]https://bugzilla.kernel.org/show_bug.cgi?id=16223
Timothy Miller <[email protected]> changed:
What |Removed |Added
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Status|RESOLVED |REOPENED
Resolution|OBSOLETE |--- Comment #1 from Timothy Miller <[email protected]> 2012-07-20 13:56:22 --- Why was this marked obsolete?
According to this documentation on kernel.org, ext4 still does not support delayed allocation in data=journal mode:
http://kernel.org/doc/Documentation/filesystems/ext4.txt
I've also spent some time googling this, and I haven't been able to find any announcement that this has been fixed.
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[Bug 16223] ext4 in data=journal mode does not support delayed allocation
In reply to [email protected]https://bugzilla.kernel.org/show_bug.cgi?id=16223
Alan <[email protected]> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|REOPENED |RESOLVED
Resolution| |OBSOLETE--- Comment #2 from Alan <[email protected]> 2012-07-20 14:01:27 --- Because its 2 years old and we don't use bugzilla to track feature wishlists
If you want it supported send patches.
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