Messages in this thread Patch in this message | | | Subject | [patch] call truncate_inode_pages in the DIO fallback to buffered I/O path | From | Jeff Moyer <> | Date | Wed, 04 Oct 2006 13:04:42 -0400 |
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Hi,
It seems that Oracle creates sparse files when doing table creates, and then populates those files using O_DIRECT I/O. That means that every I/O to the sparse file falls back to buffered I/O. Currently, such a sequential O_DIRECT write to a sparse file will end up populating the page cache. The problem is that we don't invalidate the page cache pages used to perform the buffered fallback. After talking this over with Zach, we agreed that there should be a call to truncate_inode_pages_range after the buffered I/O fallback.
Attached is a patch which addresses the problem in my testing. I wrote a simple test program that creates a sparse file and issues sequential DIO writes to it. Before the patch, the page cache would grow as the file was written. With the patch, the page cache does not grow.
Comments welcome.
Cheers,
Jeff
Signed-off-by: Jeff Moyer <jmoyer@redhat.com>
--- linux-2.6.18.i686/mm/filemap.c.orig 2006-10-02 12:59:25.000000000 -0400 +++ linux-2.6.18.i686/mm/filemap.c 2006-10-04 12:54:51.000000000 -0400 @@ -2350,7 +2350,7 @@ __generic_file_aio_write_nolock(struct k unsigned long nr_segs, loff_t *ppos) { struct file *file = iocb->ki_filp; - const struct address_space * mapping = file->f_mapping; + struct address_space * mapping = file->f_mapping; size_t ocount; /* original count */ size_t count; /* after file limit checks */ struct inode *inode = mapping->host; @@ -2417,6 +2417,15 @@ __generic_file_aio_write_nolock(struct k written = generic_file_buffered_write(iocb, iov, nr_segs, pos, ppos, count, written); + + /* + * When falling through to buffered I/O, we need to ensure that the + * page cache pages are written to disk and invalidated to preserve + * the expected O_DIRECT semantics. + */ + if (unlikely(file->f_flags & O_DIRECT)) + truncate_inode_pages_range(mapping, pos, pos + count - 1); + out: current->backing_dev_info = NULL; return written ? written : err; - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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