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SubjectBUG in fs/proc/generic.c:proc_file_read
In short:
The hack used to be able to read proc files larger than 4k, breaks if the
caller does lseek() after read()

I am providing a proc read interface to one of my proc files by using the
given hack symantics in which every call to read_proc() writes the data
starting at the begining of the page but sets "*start" artificially to
indicate how many fields have been read. proc_file_read then correctly
adjusts *ppos to signify the artificial position inside the proc file
where the read pointer points. It is *artificial* beacuse it is not the
byte offset but some other offset which only read_proc understands. Next
time around when read_proc gets the *ppos to start reading from it knows
how to calculate the exxat byte offset from the *artificial* *ppos
This works fine with cat which simply calls read(). The "more" command
though has the following call pattern

read(fd,buf,4096) = X

-- lseek modified file->f_pos to the byte offset value, which disturbed
read_proc ---

read(fd,buf,4096) = 0;

the effect is that more never gives me data more than 4096 bytes worth.

My Question is. Is it a known problem ?


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