Hi Michael,
On 02/04/2015 10:28 AM, Michael Kerrisk (man-pages) wrote:
Hello Jan,
On 18 October 2014 at 17:22, Jan Chaloupka <jchaloup@xxxxxxxxxx> wrote:
As from upstream commit:
commit 3f31d07571eeea18a7d34db9af21d2285b807a17
Author: Hugh Dickins <hughd@xxxxxxxxxx>
Date: Tue May 29 15:06:40 2012 -0700
mm/fs: route MADV_REMOVE to FALLOC_FL_PUNCH_HOLE
Now tmpfs supports hole-punching via fallocate(), switch madvise_remove()
to use do_fallocate() instead of vmtruncate_range(): which extends
madvise(,,MADV_REMOVE) support from tmpfs to ext4, ocfs2 and xfs.
madvise(,,MADV_REMOVE) support was extended by ext4, ocfs2 and xfs.
bug report: https://bugzilla.redhat.com/show_bug.cgi?id=1120294
Justification from Rafael Aquini:
Well, that code is committed in kernel since v3.5 (2012) and it surely is
the expected behaviour since. It seems to me that madvise(2) man page text
for MADV_REMOVE just got out-of-date in that regard.
This patch mentions this support in madvise.2 man page.
Reworded and corrected by Michael Kerrisk and Hugh Dickins. Thank you.
Sorry for the delay. I've applied this patch (and tweaked it a little, but
not in essential details). Not yet pushed to kernel.,org yet.
Thanks :)
Cheers,
Michael
Signed-off-by: Jan Chaloupka <jchaloup@xxxxxxxxxx>
---
man2/madvise.2 | 17 ++++++++++++-----
1 file changed, 12 insertions(+), 5 deletions(-)
diff --git a/man2/madvise.2 b/man2/madvise.2
index 032ead7..b955864 100644
--- a/man2/madvise.2
+++ b/man2/madvise.2
@@ -101,11 +101,18 @@ without an underlying file.
.BR MADV_REMOVE " (since Linux 2.6.16)"
Free up a given range of pages
and its associated backing store.
-Currently,
-.\" 2.6.18-rc5
-only shmfs/tmpfs supports this; other filesystems return with the
-error
-.BR ENOSYS .
+Originally, only shmfs/tmpfs supported this; but since Linux 3.5,
+any filesystem which supports the
+.BR fallocate(2)
+mode
+.BR FALLOC_FL_PUNCH_HOLE
+also supports the
+.BR madvise(2)
+advice
+.BR MADV_REMOVE .
+Other filesystems return with the
+.BR EOPNOTSUPP
+error.
.\" Databases want to use this feature to drop a section of their
.\" bufferpool (shared memory segments) - without writing back to
.\" disk/swap space. This feature is also useful for supporting
--
Jan Chaloupka
------------------------------
* Software Engineer *
* ENG Base Operating Systems *
* Red Hat Czech, s. r. o. *
* UTC+1 (CET), jchaloup *
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