I am currently working on a project on EXT3 filesystem in my college.

I need to trace how is the file actually written, that is, write from the VFS code upto block allocation level. For example, if you give command say "cp a.c b.c", then i need to know how is the data of the file b.c actually written and which functions are called to do so (including VFS functions such as vfs_write(), do_sync_write() )

So far, i have tried putting printk() and traceflags in respective files for ext3. I have also tried the same for file "fs/read_write.c". It has helped me reach to vfs_write() and do_sync_write in fs/read_write.c

But i am unable to find the EXACT flow from VFS.

In addition, can anyone please tell me the function used by VFS to write into a file....

I need to modify the writing strategy. For that i need the above function.

Kindly help,
Zishan Shaikh.

I think you best get hold of a copy of "Understanding the Linux Kernel" (ULK3) and check chapter 16.1: "Reading and Writing a File".

I had read that chapter already but had not understood when i had read earlier. Now when i got used to the variables used in the code and the chapter, i read that entire chapter thrice to get the exact flow. The problem is solved. I have successfully found where EXT3 actually allocates the blocks, thanks to the flow of how the data is written to the disk through VFS.
Thank you,
Zishan.