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SubjectRe: [PATCH v3 2/2] io_uring: add support for IORING_OP_GETDENTS
On Thu, Feb 18, 2021 at 02:27:55PM +0200, Lennert Buytenhek wrote:
> IORING_OP_GETDENTS may or may not update the specified directory's
> file offset, and the file offset should not be relied upon having
> any particular value during or after an IORING_OP_GETDENTS call.

This doesn't give me the warm fuzzies. What I might suggest
is either passing a parameter to iterate_dir() or breaking out an
iterate_dir_nofpos() to make IORING_OP_GETDENTS more of a READV operation.
ie the equivalent of this:

@@ -37,7 +37,7 @@
} while (0)


-int iterate_dir(struct file *file, struct dir_context *ctx)
+int iterate_dir(struct file *file, struct dir_context *ctx, bool use_fpos)
{
struct inode *inode = file_inode(file);
bool shared = false;
@@ -60,12 +60,14 @@ int iterate_dir(struct file *file, struct dir_context *ctx)

res = -ENOENT;
if (!IS_DEADDIR(inode)) {
- ctx->pos = file->f_pos;
+ if (use_fpos)
+ ctx->pos = file->f_pos;
if (shared)
res = file->f_op->iterate_shared(file, ctx);
else
res = file->f_op->iterate(file, ctx);
- file->f_pos = ctx->pos;
+ if (use_fpos)
+ file->f_pos = ctx->pos;
fsnotify_access(file);
file_accessed(file);
}
That way there's no need to play with llseek or take a mutex on the
f_pos of the directory.

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