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| author |   Al Viro <viro@zeniv.linux.org.uk> | 2016-01-14 17:52:59 -0500 |
|---|---|---|
| committer | Al Viro <viro@zeniv.linux.org.uk> | 2016-01-14 17:56:54 -0500 |
| commit | e8ecde25f5e08f89b61d86c32bbb56b405e90c32 (patch) | |
| tree | 826e424c86cd079b845ad497bd8c9867b490524f | |
| parent | Merge tag 'upstream-4.5-rc1' of git://git.infradead.org/linux-ubifs (diff) | |
| download | linux-dev-e8ecde25f5e08f89b61d86c32bbb56b405e90c32.tar.xz linux-dev-e8ecde25f5e08f89b61d86c32bbb56b405e90c32.zip | |
Make sure that highmem pages are not added to symlink page cache
inode_nohighmem() is sufficient to make sure that page_get_link()
won't try to allocate a highmem page. Moreover, it is sufficient
to make sure that page_symlink/__page_symlink won't do the same
thing. However, any filesystem that manually preseeds the symlink's
page cache upon symlink(2) needs to make sure that the page it
inserts there won't be a highmem one.
Fortunately, only nfs and shmem have run afoul of that...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
| -rw-r--r-- | Documentation/filesystems/porting | 6 | ||||
| -rw-r--r-- | fs/nfs/dir.c | 5 | ||||
| -rw-r--r-- | mm/shmem.c | 2 |
3 files changed, 8 insertions, 5 deletions
diff --git a/Documentation/filesystems/porting b/Documentation/filesystems/porting index 0f88e6020487..f1b87d8aa2da 100644 --- a/Documentation/filesystems/porting +++ b/Documentation/filesystems/porting @@ -508,7 +508,11 @@ in your dentry operations instead. [mandatory] any symlink that might use page_follow_link_light/page_put_link() must have inode_nohighmem(inode) called before anything might start playing with - its pagecache. + its pagecache. No highmem pages should end up in the pagecache of such + symlinks. That includes any preseeding that might be done during symlink + creation. __page_symlink() will honour the mapping gfp flags, so once + you've done inode_nohighmem() it's safe to use, but if you allocate and + insert the page manually, make sure to use the right gfp flags. -- [mandatory] ->follow_link() is replaced with ->get_link(); same API, except that diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c index ce5a21861074..8a0530921685 100644 --- a/fs/nfs/dir.c +++ b/fs/nfs/dir.c @@ -1894,15 +1894,14 @@ int nfs_symlink(struct inode *dir, struct dentry *dentry, const char *symname) attr.ia_mode = S_IFLNK | S_IRWXUGO; attr.ia_valid = ATTR_MODE; - page = alloc_page(GFP_HIGHUSER); + page = alloc_page(GFP_USER); if (!page) return -ENOMEM; - kaddr = kmap_atomic(page); + kaddr = page_address(page); memcpy(kaddr, symname, pathlen); if (pathlen < PAGE_SIZE) memset(kaddr + pathlen, 0, PAGE_SIZE - pathlen); - kunmap_atomic(kaddr); trace_nfs_symlink_enter(dir, dentry); error = NFS_PROTO(dir)->symlink(dir, dentry, page, pathlen, &attr); diff --git a/mm/shmem.c b/mm/shmem.c index 5813b7fa85b6..642471b0ddea 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -2469,6 +2469,7 @@ static int shmem_symlink(struct inode *dir, struct dentry *dentry, const char *s inode->i_op = &shmem_short_symlink_operations; inode->i_link = info->symlink; } else { + inode_nohighmem(inode); error = shmem_getpage(inode, 0, &page, SGP_WRITE, NULL); if (error) { iput(inode); @@ -2476,7 +2477,6 @@ static int shmem_symlink(struct inode *dir, struct dentry *dentry, const char *s } inode->i_mapping->a_ops = &shmem_aops; inode->i_op = &shmem_symlink_inode_operations; - inode_nohighmem(inode); memcpy(page_address(page), symname, len); SetPageUptodate(page); set_page_dirty(page); |