Re: [PATCH v4 03/11] fs: Initial atomic write support

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Helper function atomic_write_valid() can be used by FSes to verify
compliant writes.

Signed-off-by: Prasad Singamsetty <prasad.singamsetty@xxxxxxxxxx>
#jpg: merge into single patch and much rewrite

^^^ this might be a miss I guess.

I'm not sure what you mean. Here I am just briefly commenting on much changes which I made.

Signed-off-by: John Garry <john.g.garry@xxxxxxxxxx>
  fs/aio.c                |  8 ++++----
  fs/btrfs/ioctl.c        |  2 +-
  fs/read_write.c         |  2 +-
  include/linux/fs.h      | 36 +++++++++++++++++++++++++++++++++++-
  include/uapi/linux/fs.h |  5 ++++-
  io_uring/rw.c           |  4 ++--
  6 files changed, 47 insertions(+), 10 deletions(-)

diff --git a/fs/aio.c b/fs/aio.c
index bb2ff48991f3..21bcbc076fd0 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -1502,7 +1502,7 @@ static void aio_complete_rw(struct kiocb *kiocb, long res)
-static int aio_prep_rw(struct kiocb *req, const struct iocb *iocb)
+static int aio_prep_rw(struct kiocb *req, const struct iocb *iocb, int type)

maybe rw_type?


  	int ret;
@@ -1528,7 +1528,7 @@ static int aio_prep_rw(struct kiocb *req, const struct iocb *iocb)
  	} else


  /* 32bit hashes as llseek() offset (for directories) */
  #define FMODE_32BITHASH         ((__force fmode_t)0x200)
  /* 64bit hashes as llseek() offset (for directories) */
@@ -328,6 +333,7 @@ enum rw_hint {
  #define IOCB_SYNC		(__force int) RWF_SYNC
  #define IOCB_NOWAIT		(__force int) RWF_NOWAIT
  #define IOCB_APPEND		(__force int) RWF_APPEND
+#define IOCB_ATOMIC		(__force int) RWF_ATOMIC

You might also want to add this definition in here too



I suppose that new flag RWF_NOAPPEND in linux-next also should have this

+static inline bool atomic_write_valid(loff_t pos, struct iov_iter *iter,
+			   unsigned int unit_min, unsigned int unit_max)
+	size_t len = iov_iter_count(iter);
+	if (!iter_is_ubuf(iter))
+		return false;

There is no mention about this limitation in the commit message of this
patch. Maybe it will be good to capture why this limitation to only
support ubuf and/or any plans to lift this restriction in future
in the commit message?

ok, I can mention this in the commit message.

+	if (len == unit_min || len == unit_max) {
+		/* ok if exactly min or max */
+	} else if (len < unit_min || len > unit_max) {
+		return false;
+	} else if (!is_power_of_2(len)) {
+		return false;
+	}

Checking for len == unit_min || len == unit_max is redundant when
unit_min and unit_max are already power of 2.

Sure, but it was an optimization, considering that typically we will be issuing unit_max in anticipated FS scenario.

Anyway, I will be changing this according to an earlier comment.


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