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Hi! > > > > Do you mean calling sys_sync() after the userspace has been frozen > > > > may not be sufficient? > > > > > > In most cases it probably is, but sys_sync() doesn't provide any > > > guarantees that the filesystem is not being used or written to after > > > it completes. Given that every so often I hear about an XFS filesystem > > > that was corrupted by suspend, I don't think this is sufficient... > > > > Userspace is frozen. There's noone that can write to the XFS > > filesystem. > > Sure, no new userspace processes can write data, but what about the > internal state of the filesystem? > > All a sync guarantees is that the filesystem is consistent when the > sync returns and XFS provides this guarantee by writing all data and > ensuring all metadata changes are logged so if a crash occurs it can > be recovered (which provides the sync guarantee). hence after a > sys_sync(), XFS will still have lots of dirty metadata that needs to > be written to disk at some time in the future so the transactions > can be removed from the log. > > This dirty metadata can be flushed at any time, and the dirty state > is kept in XFS structures and not always in page structures (think > multipage metadata buffers). Hence I cannot see how suspend can > guarantee that it has saved all the dirty data in XFS, nor > restore it correctly on resume. Once you toss dirty metadata that > is currently in the log, further operations will result in that log > transaction being overwritten without it ever being written to disk. > That then means any subsequent operations after resume will corrupt > the filesystem.... > > Hence the only way to correctly rebuild the XFS state on resume is > to quiesce the filesystem on suspend and thaw it on resume so as to > trigger log recovery. No, during suspend/resume, memory image is saved, and no state is lost. We would not even have to do sys_sync(), and suspend/resume would still work properly. sys_sync() is there only to limit damage in case of suspend/resume failure. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ | ||||||||||||
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