From: Christoph Hellwig <email@example.com> To: "Darrick J. Wong" <firstname.lastname@example.org> Cc: email@example.com, firstname.lastname@example.org Subject: Re: [PATCH 2/2] xfs: relax unwritten writeback overhead under some circumstances Date: Thu, 16 Jan 2020 08:49:00 -0800 Message-ID: <20200116164900.GB4593@infradead.org> (raw) In-Reply-To: <157915535801.2406747.10502356876965505327.stgit@magnolia> On Wed, Jan 15, 2020 at 10:15:58PM -0800, Darrick J. Wong wrote: > From: Darrick J. Wong <email@example.com> > > In the previous patch, we solved a stale disk contents exposure problem > by forcing the delalloc write path to create unwritten extents, write > the data, and convert the extents to written after writeback completes. > > This is a pretty huge hammer to use, so we'll relax the delalloc write > strategy to go straight to written extents (as we once did) if someone > tells us to write the entire file to disk. This reopens the exposure > window slightly, but we'll only be affected if writeback completes out > of order and the system crashes during writeback. > > Because once again we can map written extents past EOF, we also > enlarge the writepages window downward if the window is beyond the > on-disk size and there are written extents after the EOF block. This > ensures that speculative post-EOF preallocations are not left uncovered. This does sound really sketchy. Do you have any performance numbers justifying something this nasty?
next prev parent reply index Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-01-16 6:15 [PATCH 0/2] xfs: fix stale disk exposure after crash Darrick J. Wong 2020-01-16 6:15 ` [PATCH 1/2] xfs: force writes to delalloc regions to unwritten Darrick J. Wong 2020-01-16 16:47 ` Christoph Hellwig 2020-01-16 23:16 ` Darrick J. Wong 2020-01-19 20:49 ` Dave Chinner 2020-01-16 6:15 ` [PATCH 2/2] xfs: relax unwritten writeback overhead under some circumstances Darrick J. Wong 2020-01-16 16:49 ` Christoph Hellwig [this message] 2020-01-16 23:15 ` Darrick J. Wong 2020-01-16 16:49 ` [PATCH 0/2] xfs: fix stale disk exposure after crash Christoph Hellwig 2020-01-16 23:00 ` Darrick J. Wong
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