From fc5e58c0c4fd86881ec8ba8e46e41a07e25dc7a6 Mon Sep 17 00:00:00 2001
From: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Date: Thu, 24 Mar 2011 16:14:26 +0200
Subject: UBIFS: use GFP_NOFS properly

This patch fixes a brown-paperbag bug which was introduced by me:
I used incorrect "GFP_KERNEL | GFP_NOFS" allocation flags to make
sure my allocations do not cause write-back. But the correct form
is "GFP_NOFS".

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
---
 fs/ubifs/debug.c      | 2 +-
 fs/ubifs/lprops.c     | 2 +-
 fs/ubifs/lpt_commit.c | 4 ++--
 fs/ubifs/orphan.c     | 2 +-
 4 files changed, 5 insertions(+), 5 deletions(-)

(limited to 'fs')

diff --git a/fs/ubifs/debug.c b/fs/ubifs/debug.c
index 01c2b028e525..f25a7339f800 100644
--- a/fs/ubifs/debug.c
+++ b/fs/ubifs/debug.c
@@ -818,7 +818,7 @@ void dbg_dump_leb(const struct ubifs_info *c, int lnum)
 	printk(KERN_DEBUG "(pid %d) start dumping LEB %d\n",
 	       current->pid, lnum);
 
-	buf = __vmalloc(c->leb_size, GFP_KERNEL | GFP_NOFS, PAGE_KERNEL);
+	buf = __vmalloc(c->leb_size, GFP_NOFS, PAGE_KERNEL);
 	if (!buf) {
 		ubifs_err("cannot allocate memory for dumping LEB %d", lnum);
 		return;
diff --git a/fs/ubifs/lprops.c b/fs/ubifs/lprops.c
index c7b25e2f7764..0ee0847f2421 100644
--- a/fs/ubifs/lprops.c
+++ b/fs/ubifs/lprops.c
@@ -1094,7 +1094,7 @@ static int scan_check_cb(struct ubifs_info *c,
 		}
 	}
 
-	buf = __vmalloc(c->leb_size, GFP_KERNEL | GFP_NOFS, PAGE_KERNEL);
+	buf = __vmalloc(c->leb_size, GFP_NOFS, PAGE_KERNEL);
 	if (!buf) {
 		ubifs_err("cannot allocate memory to scan LEB %d", lnum);
 		goto out;
diff --git a/fs/ubifs/lpt_commit.c b/fs/ubifs/lpt_commit.c
index 0a3c2c3f5c4a..0c9c69bd983a 100644
--- a/fs/ubifs/lpt_commit.c
+++ b/fs/ubifs/lpt_commit.c
@@ -1633,7 +1633,7 @@ static int dbg_check_ltab_lnum(struct ubifs_info *c, int lnum)
 	if (!(ubifs_chk_flags & UBIFS_CHK_LPROPS))
 		return 0;
 
-	buf = p = __vmalloc(c->leb_size, GFP_KERNEL | GFP_NOFS, PAGE_KERNEL);
+	buf = p = __vmalloc(c->leb_size, GFP_NOFS, PAGE_KERNEL);
 	if (!buf) {
 		ubifs_err("cannot allocate memory for ltab checking");
 		return 0;
@@ -1885,7 +1885,7 @@ static void dump_lpt_leb(const struct ubifs_info *c, int lnum)
 
 	printk(KERN_DEBUG "(pid %d) start dumping LEB %d\n",
 	       current->pid, lnum);
-	buf = p = __vmalloc(c->leb_size, GFP_KERNEL | GFP_NOFS, PAGE_KERNEL);
+	buf = p = __vmalloc(c->leb_size, GFP_NOFS, PAGE_KERNEL);
 	if (!buf) {
 		ubifs_err("cannot allocate memory to dump LPT");
 		return;
diff --git a/fs/ubifs/orphan.c b/fs/ubifs/orphan.c
index 2cdbd31641d7..09df318e368f 100644
--- a/fs/ubifs/orphan.c
+++ b/fs/ubifs/orphan.c
@@ -898,7 +898,7 @@ static int dbg_scan_orphans(struct ubifs_info *c, struct check_info *ci)
 	if (c->no_orphs)
 		return 0;
 
-	buf = __vmalloc(c->leb_size, GFP_KERNEL | GFP_NOFS, PAGE_KERNEL);
+	buf = __vmalloc(c->leb_size, GFP_NOFS, PAGE_KERNEL);
 	if (!buf) {
 		ubifs_err("cannot allocate memory to check orphans");
 		return 0;
-- 
cgit v1.2.3


From 9d523cafbe0dab5a2b873ecd85c37fec9d1368f3 Mon Sep 17 00:00:00 2001
From: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Date: Mon, 21 Mar 2011 16:16:29 +0200
Subject: UBIFS: kill CONFIG_UBIFS_FS_DEBUG_CHKS

Simplify UBIFS configuration menu and kill the option to enable self-check
compile-time. We do not really need this because we can do this run-time
using the module parameters or the corresponding sysfs interfaces. And
there is a value in simplifying the kernel configuration menu which becomes
increasingly large.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
---
 fs/ubifs/Kconfig | 9 ---------
 1 file changed, 9 deletions(-)

(limited to 'fs')

diff --git a/fs/ubifs/Kconfig b/fs/ubifs/Kconfig
index 1d1859dc3de5..d7440904be17 100644
--- a/fs/ubifs/Kconfig
+++ b/fs/ubifs/Kconfig
@@ -58,12 +58,3 @@ config UBIFS_FS_DEBUG
 	  down UBIFS. You can then further enable / disable individual  debugging
 	  features using UBIFS module parameters and the corresponding sysfs
 	  interfaces.
-
-config UBIFS_FS_DEBUG_CHKS
-	bool "Enable extra checks"
-	depends on UBIFS_FS_DEBUG
-	help
-	  If extra checks are enabled UBIFS will check the consistency of its
-	  internal data structures during operation. However, UBIFS performance
-	  is dramatically slower when this option is selected especially if the
-	  file system is large.
-- 
cgit v1.2.3


From 6ed09c34b7984a978a73a855f4c2e6662acc8bdb Mon Sep 17 00:00:00 2001
From: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Date: Wed, 23 Mar 2011 10:32:58 +0200
Subject: UBIFS: fix assertion warning and refine comments

This patch fixes the following UBIFS assertion warning:

UBIFS assert failed in do_readpage at 115 (pid 199)
[<b00321b8>] (unwind_backtrace+0x0/0xdc) from [<af025118>]
(do_readpage+0x108/0x594 [ubifs])
[<af025118>] (do_readpage+0x108/0x594 [ubifs]) from [<af025764>]
(ubifs_write_end+0x1c0/0x2e8 [ubifs])
[<af025764>] (ubifs_write_end+0x1c0/0x2e8 [ubifs]) from
[<b00a0164>] (generic_file_buffered_write+0x18c/0x270)
[<b00a0164>] (generic_file_buffered_write+0x18c/0x270) from
[<b00a08d4>] (__generic_file_aio_write+0x478/0x4c0)
[<b00a08d4>] (__generic_file_aio_write+0x478/0x4c0) from
[<b00a0984>] (generic_file_aio_write+0x68/0xc8)
[<b00a0984>] (generic_file_aio_write+0x68/0xc8) from
[<af024a78>] (ubifs_aio_write+0x178/0x1d8 [ubifs])
[<af024a78>] (ubifs_aio_write+0x178/0x1d8 [ubifs]) from
[<b00d104c>] (do_sync_write+0xb0/0x100)
[<b00d104c>] (do_sync_write+0xb0/0x100) from [<b00d1abc>]
(vfs_write+0xac/0x154)
[<b00d1abc>] (vfs_write+0xac/0x154) from [<b00d1c10>]
(sys_write+0x3c/0x68)
[<b00d1c10>] (sys_write+0x3c/0x68) from [<b002d9a0>]
(ret_fast_syscall+0x0/0x2c)

The 'PG_checked' flag is used to indicate that the page does not
supposedly exist on the media (e.g., a hole or a page beyond the
inode size), so it requires slightly bigger budget, because we have
to account the indexing size increase. And this flag basically
tells that the budget for this page has to be "new page budget".
The "new page budget" is slightly bigger than the "existing page
budget".

The 'do_readpage()' function has the following assertion which
sometimes is hit: 'ubifs_assert(!PageChecked(page))'. Obviously,
the meaning of this assertion is: "I should not be asked to read
a page which does not exist on the media".

However, in 'ubifs_write_begin()' we have a small "trick". Notice,
that VFS may write pages which were not read yet, so the page data
were not loaded from the media to the page cache yet. If VFS tells
that it is going to change only some part of the page, we obviously
have to load it from the media. However, if VFS tells that it is
going to change whole page, we do not read it from the media for
optimization purposes.

However, since we do not read it, we do not know if it exists on
the media or not (a hole, etc). So we set the 'PG_checked' flag
to this page to force bigger budget, just in case.

So 'ubifs_write_begin()' sets 'PG_checked'. Then we are in
'ubifs_write_end()'. And VFS tells us: "hey, for some reasons I
changed my mind and did not change whole page". Frankly, I do not
know why this happens, but I hit this somehow on an ARM platform.
And this is extremely rare.

So in this case UBIFS does the following:

1. Cancels allocated budget.
2. Loads the page from the media by calling 'do_readpage()'.
3. Asks VFS to repeat the whole write operation from the very
   beginning (call '->write_begin() again, etc).

And the assertion warning is hit at the step 2 - remember we have
the 'PG_checked' set for this page, and 'do_readpage()' does not
like this. So this patch fixes the problem by adding step 1.5 and
cleaning the 'PG_checked' before calling 'do_readpage()'.

All in all, this patch does not fix any functionality issue, but it
silences UBIFS false positive warning which may happen in very very
rare cases.

And while on it, this patch also improves a commentary which explains
the reasons of setting the 'PG_checked' flag for the page. The old
commentary was a bit difficult to understand.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
---
 fs/ubifs/file.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

(limited to 'fs')

diff --git a/fs/ubifs/file.c b/fs/ubifs/file.c
index d77db7e36484..28be1e6a65e8 100644
--- a/fs/ubifs/file.c
+++ b/fs/ubifs/file.c
@@ -448,10 +448,12 @@ static int ubifs_write_begin(struct file *file, struct address_space *mapping,
 		if (!(pos & ~PAGE_CACHE_MASK) && len == PAGE_CACHE_SIZE) {
 			/*
 			 * We change whole page so no need to load it. But we
-			 * have to set the @PG_checked flag to make the further
-			 * code know that the page is new. This might be not
-			 * true, but it is better to budget more than to read
-			 * the page from the media.
+			 * do not know whether this page exists on the media or
+			 * not, so we assume the latter because it requires
+			 * larger budget. The assumption is that it is better
+			 * to budget a bit more than to read the page from the
+			 * media. Thus, we are setting the @PG_checked flag
+			 * here.
 			 */
 			SetPageChecked(page);
 			skipped_read = 1;
@@ -559,6 +561,7 @@ static int ubifs_write_end(struct file *file, struct address_space *mapping,
 		dbg_gen("copied %d instead of %d, read page and repeat",
 			copied, len);
 		cancel_budget(c, page, ui, appending);
+		ClearPageChecked(page);
 
 		/*
 		 * Return 0 to force VFS to repeat the whole operation, or the
-- 
cgit v1.2.3