On Sun, Jun 02, 2024 at 09:42:38PM +0100, Al Viro wrote:
> We never had callers for __close_range() except for close_range(2)
> itself. Nothing of that sort has appeared in four years and if any users
> do show up, we can always separate those suckers again.
BTW, looking through close_range()... We have
static unsigned int sane_fdtable_size(struct fdtable *fdt, unsigned int max_fds)
{
unsigned int count;
count = count_open_files(fdt);
if (max_fds < NR_OPEN_DEFAULT)
max_fds = NR_OPEN_DEFAULT;
return ALIGN(min(count, max_fds), BITS_PER_LONG);
}
which decides how large a table would be needed for descriptors below max_fds
that are opened in fdt. And we start with finding the last opened descriptor
in fdt (well, rounded up to BITS_PER_LONG, if you look at count_open_files()).
Why do we bother to look at _anything_ past the max_fds? Does anybody have
objections to the following?
diff --git a/fs/file.c b/fs/file.c
index f9fcebc7c838..4976ede108e0 100644
--- a/fs/file.c
+++ b/fs/file.c
@@ -276,20 +276,6 @@ static inline bool fd_is_open(unsigned int fd, const struct fdtable *fdt)
return test_bit(fd, fdt->open_fds);
}
-static unsigned int count_open_files(struct fdtable *fdt)
-{
- unsigned int size = fdt->max_fds;
- unsigned int i;
-
- /* Find the last open fd */
- for (i = size / BITS_PER_LONG; i > 0; ) {
- if (fdt->open_fds[--i])
- break;
- }
- i = (i + 1) * BITS_PER_LONG;
- return i;
-}
-
/*
* Note that a sane fdtable size always has to be a multiple of
* BITS_PER_LONG, since we have bitmaps that are sized by this.
@@ -305,12 +291,18 @@ static unsigned int count_open_files(struct fdtable *fdt)
*/
static unsigned int sane_fdtable_size(struct fdtable *fdt, unsigned int max_fds)
{
- unsigned int count;
+ const unsigned int min_words = BITS_TO_LONGS(NR_OPEN_DEFAULT); // 1
+ unsigned int words;
+
+ if (max_fds <= NR_OPEN_DEFAULT)
+ return NR_OPEN_DEFAULT;
+
+ words = BITS_TO_LONGS(min(max_fds, fdt->max_fds)); // >= min_words
+
+ while (words > min_words && !fdt->open_fds[words - 1])
+ words--;
- count = count_open_files(fdt);
- if (max_fds < NR_OPEN_DEFAULT)
- max_fds = NR_OPEN_DEFAULT;
- return ALIGN(min(count, max_fds), BITS_PER_LONG);
+ return words * BITS_PER_LONG;
}
/*
