path: root/mm
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authorRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>2013-05-24 15:55:29 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-06-07 12:49:21 -0700
commitc846d9bcb65f83a639709904af076ad82811156f (patch)
treed3f2cc13913072c7f3118b93aa9f57274f7c38ee /mm
parent954dc41937054d91766387ea2af400c185a1e96a (diff)
nilfs2: fix issue of nilfs_set_page_dirty() for page at EOF boundary
commit 136e8770cd5d1fe38b3c613100dd6dc4db6d4fa6 upstream. nilfs2: fix issue of nilfs_set_page_dirty for page at EOF boundary DESCRIPTION: There are use-cases when NILFS2 file system (formatted with block size lesser than 4 KB) can be remounted in RO mode because of encountering of "broken bmap" issue. The issue was reported by Anthony Doggett <Anthony2486@interfaces.org.uk>: "The machine I've been trialling nilfs on is running Debian Testing, Linux version 3.2.0-4-686-pae (debian-kernel@lists.debian.org) (gcc version 4.6.3 (Debian 4.6.3-14) ) #1 SMP Debian 3.2.35-2), but I've also reproduced it (identically) with Debian Unstable amd64 and Debian Experimental (using the 3.8-trunk kernel). The problematic partitions were formatted with "mkfs.nilfs2 -b 1024 -B 8192"." SYMPTOMS: (1) System log contains error messages likewise: [63102.496756] nilfs_direct_assign: invalid pointer: 0 [63102.496786] NILFS error (device dm-17): nilfs_bmap_assign: broken bmap (inode number=28) [63102.496798] [63102.524403] Remounting filesystem read-only (2) The NILFS2 file system is remounted in RO mode. REPRODUSING PATH: (1) Create volume group with name "unencrypted" by means of vgcreate utility. (2) Run script (prepared by Anthony Doggett <Anthony2486@interfaces.org.uk>): ----------------[BEGIN SCRIPT]-------------------- VG=unencrypted lvcreate --size 2G --name ntest $VG mkfs.nilfs2 -b 1024 -B 8192 /dev/mapper/$VG-ntest mkdir /var/tmp/n mkdir /var/tmp/n/ntest mount /dev/mapper/$VG-ntest /var/tmp/n/ntest mkdir /var/tmp/n/ntest/thedir cd /var/tmp/n/ntest/thedir sleep 2 date darcs init sleep 2 dmesg|tail -n 5 date darcs whatsnew || true date sleep 2 dmesg|tail -n 5 ----------------[END SCRIPT]-------------------- REPRODUCIBILITY: 100% INVESTIGATION: As it was discovered, the issue takes place during segment construction after executing such sequence of user-space operations: open("_darcs/index", O_RDWR|O_CREAT|O_NOCTTY, 0666) = 7 fstat(7, {st_mode=S_IFREG|0644, st_size=0, ...}) = 0 ftruncate(7, 60) The error message "NILFS error (device dm-17): nilfs_bmap_assign: broken bmap (inode number=28)" takes place because of trying to get block number for third block of the file with logical offset #3072 bytes. As it is possible to see from above output, the file has 60 bytes of the whole size. So, it is enough one block (1 KB in size) allocation for the whole file. Trying to operate with several blocks instead of one takes place because of discovering several dirty buffers for this file in nilfs_segctor_scan_file() method. The root cause of this issue is in nilfs_set_page_dirty function which is called just before writing to an mmapped page. When nilfs_page_mkwrite function handles a page at EOF boundary, it fills hole blocks only inside EOF through __block_page_mkwrite(). The __block_page_mkwrite() function calls set_page_dirty() after filling hole blocks, thus nilfs_set_page_dirty function (= a_ops->set_page_dirty) is called. However, the current implementation of nilfs_set_page_dirty() wrongly marks all buffers dirty even for page at EOF boundary. As a result, buffers outside EOF are inconsistently marked dirty and queued for write even though they are not mapped with nilfs_get_block function. FIX: This modifies nilfs_set_page_dirty() not to mark hole blocks dirty. Thanks to Vyacheslav Dubeyko for his effort on analysis and proposals for this issue. Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp> Reported-by: Anthony Doggett <Anthony2486@interfaces.org.uk> Reported-by: Vyacheslav Dubeyko <slava@dubeyko.com> Cc: Vyacheslav Dubeyko <slava@dubeyko.com> Tested-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'mm')
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