Some questions about page cache

[Hao-Ran Liu]

Dear All,

I read kernel 2.6.9 page cache code and have some questions.

1. Is the call to filemap_fdatawrite() in sys_fsync() redundant? Since
sys_fsync() will call file->f_op->fsync(), and, both filemap_fdatawrite()and
file->f_op->fsync() (ext2, for example) eventually call do_writepages()
function.

2. for ext2, the purpose of sync_mapping_buffers() is to write out all
indirect blocks of an address_space, which is called by ext2_sync_file().
How do these buffers got synced when a user program called sys_sync()? I
don't find any call to ext2_sync_file() by sys_sync(). If
sync_mapping_buffers() is not needed for sys_sync(), then this should apply
for ext2_sync_file(), too?

Regards,
Hao-Ran Liu



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