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Subject[PATCH 3/2] fs: simplify get_filesystem_list / get_all_fs_names
Just output the '\0' separate list of supported file systems for block
devices directly rather than going through a pointless round of string
manipulation.

Based on an earlier patch from Al Viro <viro@zeniv.linux.org.uk>.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
fs/filesystems.c | 24 ++++++++++++++----------
include/linux/fs.h | 2 +-
init/do_mounts.c | 20 +-------------------
3 files changed, 16 insertions(+), 30 deletions(-)

diff --git a/fs/filesystems.c b/fs/filesystems.c
index 90b8d879fbaf..7c136251607a 100644
--- a/fs/filesystems.c
+++ b/fs/filesystems.c
@@ -209,21 +209,25 @@ SYSCALL_DEFINE3(sysfs, int, option, unsigned long, arg1, unsigned long, arg2)
}
#endif

-int __init get_filesystem_list(char *buf)
+void __init list_bdev_fs_names(char *buf, size_t size)
{
- int len = 0;
- struct file_system_type * tmp;
+ struct file_system_type *p;
+ size_t len;

read_lock(&file_systems_lock);
- tmp = file_systems;
- while (tmp && len < PAGE_SIZE - 80) {
- len += sprintf(buf+len, "%s\t%s\n",
- (tmp->fs_flags & FS_REQUIRES_DEV) ? "" : "nodev",
- tmp->name);
- tmp = tmp->next;
+ for (p = file_systems; p; p = p->next) {
+ if (!(p->fs_flags & FS_REQUIRES_DEV))
+ continue;
+ len = strlen(p->name) + 1;
+ if (len > size) {
+ pr_warn("%s: truncating file system list\n", __func__);
+ break;
+ }
+ memcpy(buf, p->name, len);
+ buf += len;
+ size -= len;
}
read_unlock(&file_systems_lock);
- return len;
}

#ifdef CONFIG_PROC_FS
diff --git a/include/linux/fs.h b/include/linux/fs.h
index f4ed7bf1130d..cdcd7f2a2c3f 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -3624,7 +3624,7 @@ int proc_nr_dentry(struct ctl_table *table, int write,
void *buffer, size_t *lenp, loff_t *ppos);
int proc_nr_inodes(struct ctl_table *table, int write,
void *buffer, size_t *lenp, loff_t *ppos);
-int __init get_filesystem_list(char *buf);
+void __init list_bdev_fs_names(char *buf, size_t size);

#define __FMODE_EXEC ((__force int) FMODE_EXEC)
#define __FMODE_NONOTIFY ((__force int) FMODE_NONOTIFY)
diff --git a/init/do_mounts.c b/init/do_mounts.c
index bdeb90b8d669..ffbe4deeb274 100644
--- a/init/do_mounts.c
+++ b/init/do_mounts.c
@@ -348,24 +348,6 @@ static void __init split_fs_names(char *page, char *names)
*page = '\0';
}

-static void __init get_all_fs_names(char *page)
-{
- int len = get_filesystem_list(page);
- char *s = page, *p, *next;
-
- page[len] = '\0';
- for (p = page - 1; p; p = next) {
- next = strchr(++p, '\n');
- if (*p++ != '\t')
- continue;
- while ((*s++ = *p++) != '\n')
- ;
- s[-1] = '\0';
- }
-
- *s = '\0';
-}
-
static int __init do_mount_root(const char *name, const char *fs,
const int flags, const void *data)
{
@@ -415,7 +397,7 @@ void __init mount_block_root(char *name, int flags)
if (root_fs_names)
split_fs_names(fs_names, root_fs_names);
else
- get_all_fs_names(fs_names);
+ list_bdev_fs_names(fs_names, PAGE_SIZE);
retry:
for (p = fs_names; *p; p += strlen(p)+1) {
int err = do_mount_root(name, p, flags, root_mount_data);
--
2.30.2
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