]> git.proxmox.com Git - mirror_ubuntu-disco-kernel.git/commit
xfs: limit speculative prealloc near ENOSPC thresholds
authorDave Chinner <dchinner@redhat.com>
Mon, 21 Jan 2013 12:53:54 +0000 (23:53 +1100)
committerBen Myers <bpm@sgi.com>
Mon, 28 Jan 2013 18:50:50 +0000 (12:50 -0600)
commitf2a459565b02b60408f3f2e5ca992a031319712b
tree1521bd5d0e47e5bd23ecfcde1e3763a4491ed2ae
parenteb178619f930fa2ba2348de332a1ff1c66a31424
xfs: limit speculative prealloc near ENOSPC thresholds

There is a window on small filesytsems where specualtive
preallocation can be larger than that ENOSPC throttling thresholds,
resulting in specualtive preallocation trying to reserve more space
than there is space available. This causes immediate ENOSPC to be
triggered, prealloc to be turned off and flushing to occur. One the
next write (i.e. next 4k page), we do exactly the same thing, and so
effective drive into synchronous 4k writes by triggering ENOSPC
flushing on every page while in the window between the prealloc size
and the ENOSPC prealloc throttle threshold.

Fix this by checking to see if the prealloc size would consume all
free space, and throttle it appropriately to avoid premature
ENOSPC...

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Ben Myers <bpm@sgi.com>
fs/xfs/xfs_iomap.c