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authorLinus Torvalds <torvalds@linux-foundation.org>2023-08-05 21:25:01 +0200
committerChristian Brauner <brauner@kernel.org>2023-08-06 15:08:35 +0200
commit3e3271549670783be20e233a2b78a87a0b04c715 (patch)
treed69b551046ccb83118f1f84479a461956fd35e4d /fs/readdir.c
parentproc: fix missing conversion to 'iterate_shared' (diff)
downloadlinux-3e3271549670783be20e233a2b78a87a0b04c715.tar.xz
linux-3e3271549670783be20e233a2b78a87a0b04c715.zip
vfs: get rid of old '->iterate' directory operation
All users now just use '->iterate_shared()', which only takes the directory inode lock for reading. Filesystems that never got convered to shared mode now instead use a wrapper that drops the lock, re-takes it in write mode, calls the old function, and then downgrades the lock back to read mode. This way the VFS layer and other callers no longer need to care about filesystems that never got converted to the modern era. The filesystems that use the new wrapper are ceph, coda, exfat, jfs, ntfs, ocfs2, overlayfs, and vboxsf. Honestly, several of them look like they really could just iterate their directories in shared mode and skip the wrapper entirely, but the point of this change is to not change semantics or fix filesystems that haven't been fixed in the last 7+ years, but to finally get rid of the dual iterators. Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Christian Brauner <brauner@kernel.org>
Diffstat (limited to 'fs/readdir.c')
-rw-r--r--fs/readdir.c68
1 files changed, 52 insertions, 16 deletions
diff --git a/fs/readdir.c b/fs/readdir.c
index b264ce60114d..c8c46e294431 100644
--- a/fs/readdir.c
+++ b/fs/readdir.c
@@ -25,6 +25,53 @@
#include <asm/unaligned.h>
/*
+ * Some filesystems were never converted to '->iterate_shared()'
+ * and their directory iterators want the inode lock held for
+ * writing. This wrapper allows for converting from the shared
+ * semantics to the exclusive inode use.
+ */
+int wrap_directory_iterator(struct file *file,
+ struct dir_context *ctx,
+ int (*iter)(struct file *, struct dir_context *))
+{
+ struct inode *inode = file_inode(file);
+ int ret;
+
+ /*
+ * We'd love to have an 'inode_upgrade_trylock()' operation,
+ * see the comment in mmap_upgrade_trylock() in mm/memory.c.
+ *
+ * But considering this is for "filesystems that never got
+ * converted", it really doesn't matter.
+ *
+ * Also note that since we have to return with the lock held
+ * for reading, we can't use the "killable()" locking here,
+ * since we do need to get the lock even if we're dying.
+ *
+ * We could do the write part killably and then get the read
+ * lock unconditionally if it mattered, but see above on why
+ * this does the very simplistic conversion.
+ */
+ up_read(&inode->i_rwsem);
+ down_write(&inode->i_rwsem);
+
+ /*
+ * Since we dropped the inode lock, we should do the
+ * DEADDIR test again. See 'iterate_dir()' below.
+ *
+ * Note that we don't need to re-do the f_pos games,
+ * since the file must be locked wrt f_pos anyway.
+ */
+ ret = -ENOENT;
+ if (!IS_DEADDIR(inode))
+ ret = iter(file, ctx);
+
+ downgrade_write(&inode->i_rwsem);
+ return ret;
+}
+EXPORT_SYMBOL(wrap_directory_iterator);
+
+/*
* Note the "unsafe_put_user() semantics: we goto a
* label for errors.
*/
@@ -40,39 +87,28 @@
int iterate_dir(struct file *file, struct dir_context *ctx)
{
struct inode *inode = file_inode(file);
- bool shared = false;
int res = -ENOTDIR;
- if (file->f_op->iterate_shared)
- shared = true;
- else if (!file->f_op->iterate)
+
+ if (!file->f_op->iterate_shared)
goto out;
res = security_file_permission(file, MAY_READ);
if (res)
goto out;
- if (shared)
- res = down_read_killable(&inode->i_rwsem);
- else
- res = down_write_killable(&inode->i_rwsem);
+ res = down_read_killable(&inode->i_rwsem);
if (res)
goto out;
res = -ENOENT;
if (!IS_DEADDIR(inode)) {
ctx->pos = file->f_pos;
- if (shared)
- res = file->f_op->iterate_shared(file, ctx);
- else
- res = file->f_op->iterate(file, ctx);
+ res = file->f_op->iterate_shared(file, ctx);
file->f_pos = ctx->pos;
fsnotify_access(file);
file_accessed(file);
}
- if (shared)
- inode_unlock_shared(inode);
- else
- inode_unlock(inode);
+ inode_unlock_shared(inode);
out:
return res;
}