[LU-14969] Fall back to buffered I/O for unaligned direct I/O Created: 27/Aug/21  Updated: 17/Mar/22  Resolved: 17/Mar/22

Status: Resolved
Project: Lustre
Component/s: None
Affects Version/s: None
Fix Version/s: None

Type: New Feature Priority: Minor
Reporter: Patrick Farrell Assignee: Patrick Farrell
Resolution: Won't Do Votes: 0
Labels: None

Issue Links:
Related
is related to LU-13802 New i/o path: Buffered i/o as DIO Open
Rank (Obsolete): 9223372036854775807

 Description   

The SPECStorage test assumes we can do direct i/o at a 512 byte alignment boundary.  This is not the case in Lustre, since we have to be page aligned.

The easy solution is to do what GPFS and several other file systems do:
Fall back to buffered I/O in this case.  This is supported behavior in the kernel since at least 2.6.32.

 Comments   
Comment by Patrick Farrell [ 27/Aug/21 ]

"Patrick Farrell <pfarrell@whamcloud.com>" uploaded a new patch: https://review.whamcloud.com/44761/
Subject: LU-14969 llite: DIO fall back to buffered
Project: fs/lustre-release
Branch: master
Current Patch Set: 3
Commit: 40413ac53819c8f68abb9925bcc31c844b3228b0

Comment by Patrick Farrell [ 17/Mar/22 ]

This turned out to be much harder than expected, so we're just going to do unaligned direct I/O support instead, see LU-13805

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