[PATCH 1/2] man2/fallocate.2: document behavior with shared blocks

Signed-off-by: Darrick J. Wong <redacted>
---
 man2/fallocate.2 |   10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/man2/fallocate.2 b/man2/fallocate.2
index 54d6340..3ed1460 100644
--- a/man2/fallocate.2
+++ b/man2/fallocate.2

@@ -79,6 +79,16 @@ but the file size will not be changed even if
 is greater than the file size.
 Preallocating zeroed blocks beyond the end of the file in this manner
 is useful for optimizing append workloads.
+
+If the
+.B FALLOC_FL_UNSHARE
+flag is specified in
+.IR mode ,
+shared file data extents will be made private to the file to guarantee
+that a subsequent write will not fail due to lack of space.
+Typically, this will be done by performing a copy-on-write operation on
+all shared data in the file.
+This flag may not be supported by all filesystems.
 .PP
 Because allocation is done in block size chunks,
 .BR fallocate ()

Signed-off-by: Darrick J. Wong <redacted>
---
 man2/ioctl_ficlonerange.2  |    2 +-
 man2/ioctl_fideduperange.2 |   26 ++++++++++++++++++++++----
 2 files changed, 23 insertions(+), 5 deletions(-)

diff --git a/man2/ioctl_ficlonerange.2 b/man2/ioctl_ficlonerange.2
index ac0738a..0e3ae0e 100644
--- a/man2/ioctl_ficlonerange.2
+++ b/man2/ioctl_ficlonerange.2

@@ -114,7 +114,7 @@ regions in directories.
 .TP
 .B EOPNOTSUPP
 This can appear if the filesystem does not support reflinking either file
-descriptor.
+descriptor, or if either file descriptor refers to special inodes.
 .TP
 .B EPERM
 .IR dest_fd

diff --git a/man2/ioctl_fideduperange.2 b/man2/ioctl_fideduperange.2
index c52fa2a..2112d10 100644
--- a/man2/ioctl_fideduperange.2
+++ b/man2/ioctl_fideduperange.2

@@ -99,21 +99,39 @@ Each deduplication operation targets
 bytes in file descriptor
 .IR dest_fd
 at offset
-.IR logical_offset ".
+.IR dest_offset ".
 The field
 .IR reserved
 must be zero.
+During the call,
+.IR src_fd
+must be open for reading and
+.IR dest_fd
+must be open for writing.
+For any call to this ioctl, there may not be more than 65,536
+requests attached; each request may not exceed 16MiB.
+By convention, the storage used by
+.IR src_fd
+is mapped into
+.IR dest_fd
+and the previous contents in
+.IR dest_fd
+are freed.
 
 Upon successful completion of this ioctl, the number of bytes successfully
 deduplicated is returned in
 .IR bytes_deduped
 and a status code for the deduplication operation is returned in
 .IR status ".
-
+If even a single byte in the range does not match, the deduplication
+request will be ignored and
+.IR status
+set to
+.BR FILE_DEDUPE_RANGE_DIFFERS .
 The
 .IR status
 code is set to
-.B 0
+.B FILE_DEDUPE_RANGE_SAME
 for success, a negative error code in case of error, or
 .B FILE_DEDUPE_RANGE_DIFFERS
 if the data did not match.

@@ -150,7 +168,7 @@ regions in directories.
 .TP
 .B EOPNOTSUPP
 This can appear if the filesystem does not support deduplicating either file
-descriptor.
+descriptor, or if either file descriptor refers to special inodes.
 .TP
 .B EPERM
 .IR dest_fd