ata_alloc request failed

I've started to get this on one of my machines:

dma.des.no kernel log messages:
+++ /tmp/security.207mhx7D	Sun May 13 03:05:32 2007
+DOH! ata_alloc_request failed!
+FAILURE - out of memory in ata_raid_init_request
+FAILURE - out of memory in ata_raid_init_request
+FAILURE - out of memory in ata_raid_init_request
+g_vfs_done():ar0s1h[WRITE(offset=18879152128, length=16384)]error = 5
+g_vfs_done():ar0s1h[WRITE(offset=18879168512, length=16384)]error = 5
+g_vfs_done():ar0s1h[WRITE(offset=18879184896, length=16384)]error = 5

It's an amd64 box with 1 GB RAM and a very light workload, but it's
interesting to note that the failure happened about 90 seconds into
'periodic weekly' (most likely while rebuilding the locate database)

DES
-- 
Dag-Erling Smørgrav - des_at_des.no