[Linux-cachefs] fscache 2 GB file size limitation

[guomingyang]

This is due to the limitation of cachefiles module.

If you add flag O_LARGEFILE when dentry_open in cachefiles_write_page function, the problem will be fixed


2011-01-25 



guomingyang 



发件人： Eric Becker 
发送时间： 2011-01-25  03:15:34 
收件人： linux-cachefs 
抄送： 
主题： [Linux-cachefs] fscache 2 GB file size limitation 
 
I've attempted to benchmark cachefs on an ubuntu 10.04 machine using 
ext4 on / as the filesystem cache.  I've been reading files into memory 
using cat and redirecting the output to /dev/null.  This seems to 
utilize the cache just fine if the file is <= 2 GB.  However, if the 
file is anything over 2 GB, the cache is completely unused.  I'll clear 
stop cachefilesd, clear out the file system cache (rm -f -r 
/var/cache/fscache/*), and then restart cachefilesd to make sure there's 
nothing in it.  Then if I cat a 2.1 GB file to /dev/null du shows the 
/var/cache/fscache dir as a few KB large.  If I do the same thing with a 
2 GB file du shows the cache as using 2 GB of disk space.
Is this expected behavior or is there something I'm overlooking?
-Eric
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