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

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 <vlobanov@speakeasy.net>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Dipankar Sarma <dipankar@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 5 insertions, 5 deletions

diff --git a/fs/compat.c b/fs/compat.c
index b766964..0ec70e3 100644
--- a/fs/compat.c
+++ b/fs/compat.c
@@ -1679,19 +1679,19 @@ int compat_core_sys_select(int n, compat_ulong_t __user *inp,
 {
 	fd_set_bits fds;
 	char *bits;
-	int size, max_fdset, ret = -EINVAL;
+	int size, max_fds, ret = -EINVAL;
 	struct fdtable *fdt;
 
 	if (n < 0)
 		goto out_nofds;
 
-	/* max_fdset can increase, so grab it once to avoid race */
+	/* max_fds can increase, so grab it once to avoid race */
 	rcu_read_lock();
 	fdt = files_fdtable(current->files);
-	max_fdset = fdt->max_fdset;
+	max_fds = fdt->max_fds;
 	rcu_read_unlock();
-	if (n > max_fdset)
-		n = max_fdset;
+	if (n > max_fds)
+		n = max_fds;
 
 	/*
 	 * We need 6 bitmaps (in/out/ex for both incoming and outgoing),