[PATCH 1/1] tgtd: allow 'immutable' files and have them become read-only LUNs.

[ronnie sahlberg <ronniesahlberg@xxxxxxxxx>]

List, Tomo

(right list this time:-) )


Please find attached a small patch to the three bs_*.c files used for
SBC and MMC devices.
The patch changes the *_open() function in such way that if the normal
open for O_RDWR fails with EACCES,
we try to open the file with O_RDONLY instead, and set the LUN to read-only.


This allows to set the backing file to "chattr +i" for those
filesystems that support these attributes and automatically
flags them to read-only.


In particular for ISO images I find it very nice to have them set to
immutable to prevent any process from accidentally writing/modifying
them.


regards
ronnie sahlberg

From 4325f9d89ac3c76441bd3dae44491af999407654 Mon Sep 17 00:00:00 2001
From: Ronnie Sahlberg <ronniesahlberg@xxxxxxxxx>
Date: Sun, 10 Oct 2010 15:37:23 +1100
Subject: [PATCH] Update bs_*_open() to try to open the backend file in read-only mode
 in case the normal open in O_RDWR fails with EACCES.

If so, automatically flag this lun as read-only.

This allows files for read-only LUNS (read-only disk files and/or cd/dvd iso
extra attributes.

Signed-off-by: Ronnie Sahlberg <ronniesahlberg@xxxxxxxxx>
---
 usr/bs_aio.c  |    6 ++++++
 usr/bs_mmap.c |    7 ++++++-
 usr/bs_rdwr.c |    8 +++++++-
 3 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/usr/bs_aio.c b/usr/bs_aio.c
index 0d6a640..ce56b68 100644
--- a/usr/bs_aio.c
+++ b/usr/bs_aio.c
@@ -113,6 +113,12 @@ get_events:
 static int bs_aio_open(struct scsi_lu *lu, char *path, int *fd, uint64_t *size)
 {
 	*fd = backed_file_open(path, O_RDWR|O_LARGEFILE|O_DIRECT, size);
+	/* If we get access denied, try opening the file in readonly mode */
+	if (*fd == -1 && errno == EACCES) {
+		*fd = backed_file_open(path, O_RDONLY|O_LARGEFILE|O_DIRECT,
+				       size);
+		lu->attrs.readonly = 1;
+	}
 	if (*fd < 0)
 		return *fd;
 	return 0;
diff --git a/usr/bs_mmap.c b/usr/bs_mmap.c
index b62c8e6..f7718f2 100644
--- a/usr/bs_mmap.c
+++ b/usr/bs_mmap.c
@@ -78,7 +78,12 @@ static void bs_mmap_request(struct scsi_cmd *cmd)
 
 static int bs_mmap_open(struct scsi_lu *lu, char *path, int *fd, uint64_t *size)
 {
-	*fd = backed_file_open(path, O_RDWR| O_LARGEFILE, size);
+	*fd = backed_file_open(path, O_RDWR|O_LARGEFILE, size);
+	/* If we get access denied, try opening the file in readonly mode */
+	if (*fd == -1 && errno == EACCES) {
+		*fd = backed_file_open(path, O_RDONLY|O_LARGEFILE, size);
+		lu->attrs.readonly = 1;
+	}
 	if (*fd < 0)
 		return *fd;
 
diff --git a/usr/bs_rdwr.c b/usr/bs_rdwr.c
index 5d265e5..77d52e3 100644
--- a/usr/bs_rdwr.c
+++ b/usr/bs_rdwr.c
@@ -130,7 +130,13 @@ static void bs_rdwr_request(struct scsi_cmd *cmd)
 
 static int bs_rdwr_open(struct scsi_lu *lu, char *path, int *fd, uint64_t *size)
 {
-	*fd = backed_file_open(path, O_RDWR | O_LARGEFILE | lu->bsoflags, size);
+	*fd = backed_file_open(path, O_RDWR|O_LARGEFILE|lu->bsoflags, size);
+	/* If we get access denied, try opening the file in readonly mode */
+	if (*fd == -1 && errno == EACCES) {
+		*fd = backed_file_open(path, O_RDONLY|O_LARGEFILE|lu->bsoflags,
+				       size);
+		lu->attrs.readonly = 1;
+	}
 	if (*fd < 0)
 		return *fd;
 
-- 
1.7.3.1

Attachment: 0001-Update-bs_-_open-to-try-to-open-the-backend-file-in-.patch.gz
Description: GNU Zip compressed data