static struct fdtable *alloc_fdtable(int nr)
{
struct fdtable *fdt = NULL;
int nfds = 0;
fd_set *new_openset = NULL, *new_execset = NULL;
struct file **new_fds;
fdt = kzalloc(sizeof(*fdt), GFP_KERNEL);
if (!fdt)
goto out;
nfds = max_t(int, 8 * L1_CACHE_BYTES, roundup_pow_of_two(nr + 1));
if (nfds > NR_OPEN)
nfds = NR_OPEN;
new_openset = alloc_fdset(nfds);
new_execset = alloc_fdset(nfds);
if (!new_openset || !new_execset)
goto out;
fdt->open_fds = new_openset;
fdt->close_on_exec = new_execset;
fdt->max_fdset = nfds;
nfds = NR_OPEN_DEFAULT;
/*
* Expand to the max in easy steps, and keep expanding it until
* we have enough for the requested fd array size.
*/
do {
#if NR_OPEN_DEFAULT < 256
if (nfds < 256)
nfds = 256;
else
#endif
if (nfds < (PAGE_SIZE / sizeof(struct file *)))
nfds = PAGE_SIZE / sizeof(struct file *);
else {
nfds = nfds * 2;
if (nfds > NR_OPEN)
nfds = NR_OPEN;
}
} while (nfds <= nr);
new_fds = alloc_fd_array(nfds);
if (!new_fds)
goto out2;
fdt->fd = new_fds;
fdt->max_fds = nfds;
fdt->free_files = NULL;
return fdt;
out2:
nfds = fdt->max_fdset;
out:
if (new_openset)
free_fdset(new_openset, nfds);
if (new_execset)
free_fdset(new_execset, nfds);
kfree(fdt);
return NULL;
}
/*
* Expand the fdset in the files_struct. Called with the files spinlock
* held for write.
*/
int expand_fdset(struct files_struct *files, int nr)
{
fd_set *new_openset = NULL, *new_execset = NULL;
int error, nfds = 0;
error = -EMFILE;
if (files->max_fdset >= NR_OPEN || nr >= NR_OPEN)
goto out;
nfds = files->max_fdset;
spin_unlock(&files->file_lock);
/* Expand to the max in easy steps */
do {
if (nfds < (PAGE_SIZE * 8))
nfds = PAGE_SIZE * 8;
else {
nfds = nfds * 2;
if (nfds > NR_OPEN)
nfds = NR_OPEN;
}
} while (nfds <= nr);
error = -ENOMEM;
new_openset = alloc_fdset(nfds);
new_execset = alloc_fdset(nfds);
spin_lock(&files->file_lock);
if (!new_openset || !new_execset)
goto out;
error = 0;
/* Copy the existing tables and install the new pointers */
if (nfds > files->max_fdset) {
int i = files->max_fdset / (sizeof(unsigned long) * 8);
int count = (nfds - files->max_fdset) / 8;
/*
* Don't copy the entire array if the current fdset is
* not yet initialised.
*/
if (i) {
memcpy (new_openset, files->open_fds, files->max_fdset/8);
memcpy (new_execset, files->close_on_exec, files->max_fdset/8);
memset (&new_openset->fds_bits[i], 0, count);
memset (&new_execset->fds_bits[i], 0, count);
}
nfds = xchg(&files->max_fdset, nfds);
new_openset = xchg(&files->open_fds, new_openset);
new_execset = xchg(&files->close_on_exec, new_execset);
spin_unlock(&files->file_lock);
free_fdset (new_openset, nfds);
free_fdset (new_execset, nfds);
spin_lock(&files->file_lock);
return 0;
}
/* Somebody expanded the array while we slept ... */
out:
spin_unlock(&files->file_lock);
if (new_openset)
free_fdset(new_openset, nfds);
if (new_execset)
free_fdset(new_execset, nfds);
spin_lock(&files->file_lock);
return error;
}
