Re: [RFC PATCH 0/6] Do not call ->writepage[s] from direct reclaimand use a_ops->writepages() where possible

From: Christoph Hellwig
Date: Tue Jun 15 2010 - 12:45:24 EST

On Tue, Jun 15, 2010 at 06:14:19PM +0200, Andrea Arcangeli wrote:
> Again not what looks like from the stack trace. Also grepping for
> PF_MEMALLOC in fs/xfs shows nothing. In fact it's ext4_write_inode
> that skips the write if PF_MEMALLOC is set, not writepage apparently
> (only did a quick grep so I might be wrong). I suspect
> ext4_write_inode is the case I just mentioned about slab shrink, not
> ->writepage ;).
> inodes are small, it's no big deal to keep an inode pinned and not
> slab-reclaimable because dirty, while skipping real writepage in
> memory pressure could really open a regression in oom false positives!
> One pagecache much bigger than one inode and there can be plenty more
> dirty pagecache than inodes.

Btw, those comments in ext3/ext4 don't make much sense. The only
time iput_final ever calls into ->write_inode is when the filesystem
is beeing unmounted, which never happens with PF_MEMALLOC set.

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