Make the readahead path give up under memory pressure, also ensure that
readahead will not push on delalloc memory and deadlock us. This is also
a performance win under heavy load.
Date: Fri Apr 13 14:35:29 PDT 2001
Workarea: jen.americas.sgi.com:/src/lord/xfs-base
The following file(s) were checked into:
bonnie.engr.sgi.com:/isms/slinx/2.4.x-xfs
Modid: 2.4.x-xfs:slinx:92523a
linux/kernel/ksyms.c - 1.85
- Export free_shortage to modules, pagebuf wants it now.
linux/fs/xfs/xfs_buf.h - 1.72
- change xfs_baread to call pagebuf_readahead - passing in
PBF_DONT_BLOCK so that if we do come into the pagebuf_get path
from a transaction and memory pressure has suddenly increased
that we do not end up deadlocking again.
linux/include/linux/page_buf.h - 1.87
- Add flags parameter pagebuf_readahead()
linux/fs/pagebuf/page_buf.c - 1.77
- Create a readahead wrapper for pagebuf_get which is aware of memory
pressure and will not do the readahead if memory is low, i.e. don't
rob peter to pay paul.
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