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fideduperange.2: Fix the discussion of maximum sizes 

Fix the discussion of the limitations on the dest_count and
src_length parameters to the fideduperange ioctl() to reflect
what's actually in the kernel.

Reviewed-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
This commit is contained in:
Darrick J. Wong 2016-11-22 20:48:16 -08:00 committed by Michael Kerrisk
parent 5b711f5e45
commit c835f0e088
1 changed files with 17 additions and 3 deletions
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20
man2/ioctl_fideduperange.2
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@ -95,7 +95,7 @@ struct file_dedupe_range_info {
.in
Each deduplication operation targets
.IR length
.IR src_length
bytes in file descriptor
.IR dest_fd
at offset
@ -108,8 +108,15 @@ During the call,
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.
The combined size of the struct
.IR file_dedupe_range
and the struct
.IR file_dedupe_range_info
array must not exceed the system page size.
The maximum size of
.IR src_length
is filesystem dependent and is typically 16MiB.
This limit will be enforced silently by the filesystem.
By convention, the storage used by
.IR src_fd
is mapped into
@ -144,6 +151,13 @@ is set to indicate the error.
.SH ERRORS
Error codes can be one of, but are not limited to, the following:
.TP
.B ENOMEM
The kernel was unable to allocate sufficient memory to perform the
operation or
.IR dest_count
is so large that the input argument description spans more than a single
page of memory.
.TP
.B EBADF
.IR src_fd
is not open for reading;