linux.git/fs/file.c, branch v2.6.24

[PATCH] fdtable: Provide free_fdtable() wrapper

2006-12-22T16:55:50+00:00

Christoph Hellwig has expressed concerns that the recent fdtable changes
expose the details of the RCU methodology used to release no-longer-used
fdtable structures to the rest of the kernel.  The trivial patch below
addresses these concerns by introducing the appropriate free_fdtable()
calls, which simply wrap the release RCU usage.  Since free_fdtable() is a
one-liner, it makes sense to promote it to an inline helper.

Signed-off-by: Vadim Lobanov 
Cc: Christoph Hellwig 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] fdtable: Implement new pagesize-based fdtable allocator

2006-12-10T17:57:22+00:00

This patch provides an improved fdtable allocation scheme, useful for
expanding fdtable file descriptor entries.  The main focus is on the fdarray,
as its memory usage grows 128 times faster than that of an fdset.

The allocation algorithm sizes the fdarray in such a way that its memory usage
increases in easy page-sized chunks. The overall algorithm expands the allowed
size in powers of two, in order to amortize the cost of invoking vmalloc() for
larger allocation sizes. Namely, the following sizes for the fdarray are
considered, and the smallest that accommodates the requested fd count is
chosen:

    pagesize / 4
    pagesize / 2
    pagesize      <- memory allocator switch point
    pagesize * 2
    pagesize * 4
    ...etc...

Unlike the current implementation, this allocation scheme does not require a
loop to compute the optimal fdarray size, and can be done in efficient
straightline code.

Furthermore, since the fdarray overflows the pagesize boundary long before any
of the fdsets do, it makes sense to optimize run-time by allocating both
fdsets in a single swoop.  Even together, they will still be, by far, smaller
than the fdarray.  The fdtable->open_fds is now used as the anchor for the
fdset memory allocation.

Signed-off-by: Vadim Lobanov 
Cc: Christoph Hellwig 
Cc: Al Viro 
Cc: Dipankar Sarma 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] fdtable: Remove the free_files field

2006-12-10T17:57:22+00:00

An fdtable can either be embedded inside a files_struct or standalone (after
being expanded).  When an fdtable is being discarded after all RCU references
to it have expired, we must either free it directly, in the standalone case,
or free the files_struct it is contained within, in the embedded case.

Currently the free_files field controls this behavior, but we can get rid of
it entirely, as all the necessary information is already recorded.  We can
distinguish embedded and standalone fdtables using max_fds, and if it is
embedded we can divine the relevant files_struct using container_of().

Signed-off-by: Vadim Lobanov 
Cc: Christoph Hellwig 
Cc: Al Viro 
Cc: Dipankar Sarma 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] fdtable: Make fdarray and fdsets equal in size

2006-12-10T17:57:22+00:00

Currently, each fdtable supports three dynamically-sized arrays of data: the
fdarray and two fdsets.  The code allows the number of fds supported by the
fdarray (fdtable->max_fds) to differ from the number of fds supported by each
of the fdsets (fdtable->max_fdset).

In practice, it is wasteful for these two sizes to differ: whenever we hit a
limit on the smaller-capacity structure, we will reallocate the entire fdtable
and all the dynamic arrays within it, so any delta in the memory used by the
larger-capacity structure will never be touched at all.

Rather than hogging this excess, we shouldn't even allocate it in the first
place, and keep the capacities of the fdarray and the fdsets equal.  This
patch removes fdtable->max_fdset.  As an added bonus, most of the supporting
code becomes simpler.

Signed-off-by: Vadim Lobanov 
Cc: Christoph Hellwig 
Cc: Al Viro 
Cc: Dipankar Sarma 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] file: kill unnecessary timer in fdtable_defer

2006-12-07T16:39:32+00:00

free_fdtable_rc() schedules timer to reschedule fddef->wq if
schedule_work() on it returns 0.  However, schedule_work() guarantees that
the target work is executed at least once after the scheduling regardless
of its return value.  0 return simply means that the work was already
pending and thus no further action was required.

Another problem is that it used contant '5' as @expires argument to
mod_timer().

Kill unnecessary fddef->timer.

Signed-off-by: Tejun Heo 
Cc: Dipankar Sarma 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

WorkStruct: Pass the work_struct pointer instead of context data

2006-11-22T14:55:48+00:00

Pass the work_struct pointer to the work function rather than context data.
The work function can use container_of() to work out the data.

For the cases where the container of the work_struct may go away the moment the
pending bit is cleared, it is made possible to defer the release of the
structure by deferring the clearing of the pending bit.

To make this work, an extra flag is introduced into the management side of the
work_struct.  This governs auto-release of the structure upon execution.

Ordinarily, the work queue executor would release the work_struct for further
scheduling or deallocation by clearing the pending bit prior to jumping to the
work function.  This means that, unless the driver makes some guarantee itself
that the work_struct won't go away, the work function may not access anything
else in the work_struct or its container lest they be deallocated..  This is a
problem if the auxiliary data is taken away (as done by the last patch).

However, if the pending bit is *not* cleared before jumping to the work
function, then the work function *may* access the work_struct and its container
with no problems.  But then the work function must itself release the
work_struct by calling work_release().

In most cases, automatic release is fine, so this is the default.  Special
initiators exist for the non-auto-release case (ending in _NAR).


Signed-Off-By: David Howells

[PATCH] expand_fdtable(): remove pointless unlock+lock

2006-09-29T16:18:25+00:00

This unlock/lock on a super-unlikely path isn't worth the kernel text.

Cc: Vadim Lobanov 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] Clean up expand_fdtable() and expand_files()

2006-09-29T16:18:25+00:00

Perform a code cleanup against the expand_fdtable() and expand_files()
functions inside fs/file.c.  It aims to make the flow of code within these
functions simpler and easier to understand, via added comments and modest
refactoring.

Signed-off-by: Vadim Lobanov 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] alloc_fdtable() cleanup

2006-09-27T15:26:19+00:00

free_fdset(NULL, ...) is legal.

Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] alloc_fdtable() expansion fix

2006-07-12T19:52:55+00:00

We're supposed to go the next power of two if nfds==nr.

Of `nr', not of `nfsd'.

Spotted by Rene Scharfe 

Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds