Bug 1091898
| Summary: | [barrier] "cp -a" operation hangs on NFS mount, while barrier is enabled | |||
|---|---|---|---|---|
| Product: | [Community] GlusterFS | Reporter: | SATHEESARAN <sasundar> | |
| Component: | core | Assignee: | bugs <bugs> | |
| Status: | CLOSED DEFERRED | QA Contact: | SATHEESARAN <sasundar> | |
| Severity: | high | Docs Contact: | ||
| Priority: | low | |||
| Version: | mainline | CC: | amukherj, atumball, bugs, kaushal, ndevos, sankarshan, skoduri, smohan | |
| Target Milestone: | --- | Keywords: | Triaged | |
| Target Release: | --- | |||
| Hardware: | All | |||
| OS: | Linux | |||
| Whiteboard: | ||||
| Fixed In Version: | Doc Type: | Bug Fix | ||
| Doc Text: | Story Points: | --- | ||
| Clone Of: | ||||
| : | 1100590 (view as bug list) | Environment: | ||
| Last Closed: | 2017-08-10 13:01:03 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: | 1100590 | |||
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Description
SATHEESARAN
2014-04-28 09:44:32 UTC
After discussing with the NFS team, what I understood is a write from NFS would always have O_DSYNC flag set which is a sync write to glusterfs and as per the barrier class fops, we are supposed to block it if barrier is enabled. 'cp -a' eventually have writev call and because of which this gets hung. I will double confirm it with the team again and will keep posted. (In reply to Atin Mukherjee from comment #1) > After discussing with the NFS team, what I understood is a write from NFS > would always have O_DSYNC flag set which is a sync write to glusterfs [Santosh] This is not quite correct. There is no fsync call in NFS protocol. That gets converted into WRITE call with O_SYNC/O_DSYNC flags which would instruct backend to go for stable write (means flush to disk). For async WRITEs NFS does not send the FILE_SYNC. Instead it heavily depends on the NFS client VM subsystem i.e. whenever VM subsystem flushes the page caches, it would issue the NFS server the WRITE call with FILE_SYNC flag (i.e. stable write). It depends on the vm.dirty_ratio or its related VM settings. But if the file is opened with O_DIRECT, then every write would generate a NFS WRITE call with FILE_SYNC enabled. Gluster NFS sends every WRITE with size 1MB (by default). So if you write lesser data, then you may see one WRITE call with FILE_SYNC flag. > per the barrier class fops, we are supposed to block it if barrier is > enabled. 'cp -a' eventually have writev call and because of which this gets > hung. I will double confirm it with the team again and will keep posted. |