From 3d46b316bcc1ecb17f8e7874a8ec620c64864898 Mon Sep 17 00:00:00 2001 From: Artem Bityutskiy Date: Thu, 24 Mar 2011 16:09:56 +0200 Subject: [PATCH 1/4] UBI: 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 --- drivers/mtd/ubi/io.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/mtd/ubi/io.c b/drivers/mtd/ubi/io.c index aaa6e1e83b29..eededf94f5a6 100644 --- a/drivers/mtd/ubi/io.c +++ b/drivers/mtd/ubi/io.c @@ -1345,7 +1345,7 @@ int ubi_dbg_check_write(struct ubi_device *ubi, const void *buf, int pnum, if (!(ubi_chk_flags & UBI_CHK_IO)) return 0; - buf1 = __vmalloc(len, GFP_KERNEL | GFP_NOFS, PAGE_KERNEL); + buf1 = __vmalloc(len, GFP_NOFS, PAGE_KERNEL); if (!buf1) { ubi_err("cannot allocate memory to check writes"); return 0; @@ -1409,7 +1409,7 @@ int ubi_dbg_check_all_ff(struct ubi_device *ubi, int pnum, int offset, int len) if (!(ubi_chk_flags & UBI_CHK_IO)) return 0; - buf = __vmalloc(len, GFP_KERNEL | GFP_NOFS, PAGE_KERNEL); + buf = __vmalloc(len, GFP_NOFS, PAGE_KERNEL); if (!buf) { ubi_err("cannot allocate memory to check for 0xFFs"); return 0; From fc5e58c0c4fd86881ec8ba8e46e41a07e25dc7a6 Mon Sep 17 00:00:00 2001 From: Artem Bityutskiy Date: Thu, 24 Mar 2011 16:14:26 +0200 Subject: [PATCH 2/4] 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 --- 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(-) 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; From 9d523cafbe0dab5a2b873ecd85c37fec9d1368f3 Mon Sep 17 00:00:00 2001 From: Artem Bityutskiy Date: Mon, 21 Mar 2011 16:16:29 +0200 Subject: [PATCH 3/4] 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 --- fs/ubifs/Kconfig | 9 --------- 1 file changed, 9 deletions(-) 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. From 6ed09c34b7984a978a73a855f4c2e6662acc8bdb Mon Sep 17 00:00:00 2001 From: Artem Bityutskiy Date: Wed, 23 Mar 2011 10:32:58 +0200 Subject: [PATCH 4/4] 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) [] (unwind_backtrace+0x0/0xdc) from [] (do_readpage+0x108/0x594 [ubifs]) [] (do_readpage+0x108/0x594 [ubifs]) from [] (ubifs_write_end+0x1c0/0x2e8 [ubifs]) [] (ubifs_write_end+0x1c0/0x2e8 [ubifs]) from [] (generic_file_buffered_write+0x18c/0x270) [] (generic_file_buffered_write+0x18c/0x270) from [] (__generic_file_aio_write+0x478/0x4c0) [] (__generic_file_aio_write+0x478/0x4c0) from [] (generic_file_aio_write+0x68/0xc8) [] (generic_file_aio_write+0x68/0xc8) from [] (ubifs_aio_write+0x178/0x1d8 [ubifs]) [] (ubifs_aio_write+0x178/0x1d8 [ubifs]) from [] (do_sync_write+0xb0/0x100) [] (do_sync_write+0xb0/0x100) from [] (vfs_write+0xac/0x154) [] (vfs_write+0xac/0x154) from [] (sys_write+0x3c/0x68) [] (sys_write+0x3c/0x68) from [] (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 --- fs/ubifs/file.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) 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