Bug 1549231
| Summary: | Unable to resize image with preallocation=full mode | |||
|---|---|---|---|---|
| Product: | Red Hat Enterprise Linux 7 | Reporter: | Daniel Berrangé <berrange> | |
| Component: | qemu-kvm-rhev | Assignee: | Hanna Czenczek <hreitz> | |
| Status: | CLOSED ERRATA | QA Contact: | Tingting Mao <timao> | |
| Severity: | high | Docs Contact: | ||
| Priority: | high | |||
| Version: | 7.5 | CC: | berrange, chayang, coli, egallen, hhuang, hreitz, juzhang, kchamart, michen, mrezanin, mtessun, ngu, qzhang, timao, tnisan, virt-maint, ylavi | |
| Target Milestone: | rc | Keywords: | ZStream | |
| Target Release: | --- | |||
| Hardware: | Unspecified | |||
| OS: | Unspecified | |||
| Whiteboard: | ||||
| Fixed In Version: | qemu-kvm-rhev-2.12.0-1.el7 | Doc Type: | If docs needed, set a value | |
| Doc Text: | Story Points: | --- | ||
| Clone Of: | ||||
| : | 1566587 (view as bug list) | Environment: | ||
| Last Closed: | 2018-11-01 11:04:15 UTC | Type: | Bug | |
| Regression: | --- | Mount Type: | --- | |
| Documentation: | --- | CRM: | ||
| Verified Versions: | Category: | --- | ||
| oVirt Team: | --- | RHEL 7.3 requirements from Atomic Host: | ||
| Cloudforms Team: | --- | Target Upstream Version: | ||
| Embargoed: | ||||
| Bug Depends On: | ||||
| Bug Blocks: | 1537985, 1566587 | |||
Hi Daniel, I cannot reproduce the bug. The issue i met is that further extending passed, but the image is not fully allocated. It should be same issue as the bug 1537985. Version-Release number of selected component: qemu-kvm-rhev-2.10.0-21.el7 kernel-3.10.0-856.el7.x86_64 Test steps: 1. Create the image. # qemu-img create -f raw demo.img 5G Formatting 'demo.img', fmt=raw size=5368709120 2. Extend the image with 'full' mode, and the image is grown with full allocated. # qemu-img resize -f raw --preallocation=full demo.img +1G Image resized. # qemu-img map --output=json demo.img [{ "start": 0, "length": 5368709120, "depth": 0, "zero": true, "data": false, "offset": 0}, { "start": 5368709120, "length": 1073741824, "depth": 0, "zero": false, "data": true, "offset": 5368709120}] 3. Further extend the image with 'full' mode. The command passed but the image isn't grown with full allocated. # strace -e trace=lseek qemu-img resize -f raw --preallocation=full demo.img +1G lseek(10, 0, SEEK_END) = 6442450944 lseek(10, 6442450944, SEEK_SET) = 6442450944 lseek(10, 0, SEEK_END) = 7516192768 Image resized. +++ exited with 0 +++ # qemu-img map --output=json demo.img [{ "start": 0, "length": 5368709120, "depth": 0, "zero": true, "data": false, "offset": 0}, { "start": 5368709120, "length": 1073741824, "depth": 0, "zero": false, "data": true, "offset": 5368709120}, { "start": 6442450944, "length": 1073741824, "depth": 0, "zero": true, "data": false, "offset": 6442450944}] I think your result can be explained by the flawed code I identified. It sets 'result = -errno' when it gets integer wraparound. The 'lseek' syscall did not fail though, so this 'errno' value is going to be completely random garbage - in fact it could even be 'zero' in which case it will skip the preallocation logic thinking it has an error, but then return 0 from this method indicating success to the caller. Hi, Sorry, for some reason this got lost in my queue. I didn't even merge the upstream patches until now... Max Since the problem described in this bug report should be resolved in a recent advisory, it has been closed with a resolution of ERRATA. For information on the advisory, and where to find the updated files, follow the link below. If the solution does not work for you, open a new bug report. https://access.redhat.com/errata/RHBA-2018:3443 |
Description of problem: It is impossible to resize a file with preallocation=full, if its current size would correspond to a negative number when represented as an int32 eg create a 5GB raw file initially $ qemu-img create -f raw demo.img 5G Formatting 'demo.img', fmt=raw size=5368709120 We can successfully extend it one 1GB in size $ qemu-img resize -f raw --preallocation=full demo.img +1G Image resized. But trying to further extend it fails $ qemu-img resize -f raw --preallocation=full demo.img +1G qemu-img: Failed to seek to the old end of file: Invalid argument If you strace it, we can see the lseek() succeeded, despite the message $ strace -e trace=lseek qemu-img resize -f raw --preallocation=full demo.img +1G lseek(10, 0, SEEK_END) = 6442450944 lseek(10, 6442450944, SEEK_SET) = 6442450944 qemu-img: Failed to seek to the old end of file: Invalid argument +++ exited with 1 +++ The problem appears to be caused by this commit: commit d0bc9e5d5e86d5dd566e2d967af8476cee351c93 Author: Max Reitz <mreitz> Date: Tue Jun 13 22:20:58 2017 +0200 block/file-posix: Generalize raw_regular_truncate which added this bit of code to the preallocation=full + result = lseek(fd, current_length, SEEK_SET); + if (result < 0) { + result = -errno; + error_setg_errno(errp, -result, + "Failed to seek to the old end of file"); + goto out; + } + The 'result' variable here is a plain 'int', so 32-bits, causing the lseek result to overflow & wrap around. This patch is new in QEMU 2.10.0, so would be a regression compared to earlier 7.x releases. Version-Release number of selected component (if applicable): qemu-kvm-rhev-2.10.0-21.el7.x86_64