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authorJan Kara <jack@suse.cz>2012-06-12 16:20:37 +0200
committerAl Viro <viro@zeniv.linux.org.uk>2012-07-31 09:45:47 +0400
commit14da9200140f8d722ad1767dfabadebd8b34f2ad (patch)
treeea5d88b091999f7a64af0b9d335d7cad4c79edfb /mm/filemap_xip.c
parent5d37e9e6dec65cd21be68ee92de99686213e916b (diff)
downloadlinux-14da9200140f8d722ad1767dfabadebd8b34f2ad.tar.gz
fs: Protect write paths by sb_start_write - sb_end_write
There are several entry points which dirty pages in a filesystem. mmap (handled by block_page_mkwrite()), buffered write (handled by __generic_file_aio_write()), splice write (generic_file_splice_write), truncate, and fallocate (these can dirty last partial page - handled inside each filesystem separately). Protect these places with sb_start_write() and sb_end_write(). ->page_mkwrite() calls are particularly complex since they are called with mmap_sem held and thus we cannot use standard sb_start_write() due to lock ordering constraints. We solve the problem by using a special freeze protection sb_start_pagefault() which ranks below mmap_sem. BugLink: https://bugs.launchpad.net/bugs/897421 Tested-by: Kamal Mostafa <kamal@canonical.com> Tested-by: Peter M. Petrakis <peter.petrakis@canonical.com> Tested-by: Dann Frazier <dann.frazier@canonical.com> Tested-by: Massimo Morana <massimo.morana@canonical.com> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'mm/filemap_xip.c')
-rw-r--r--mm/filemap_xip.c5
1 files changed, 3 insertions, 2 deletions
diff --git a/mm/filemap_xip.c b/mm/filemap_xip.c
index 80b34ef82df..13e013b1270 100644
--- a/mm/filemap_xip.c
+++ b/mm/filemap_xip.c
@@ -402,6 +402,8 @@ xip_file_write(struct file *filp, const char __user *buf, size_t len,
loff_t pos;
ssize_t ret;
+ sb_start_write(inode->i_sb);
+
mutex_lock(&inode->i_mutex);
if (!access_ok(VERIFY_READ, buf, len)) {
@@ -412,8 +414,6 @@ xip_file_write(struct file *filp, const char __user *buf, size_t len,
pos = *ppos;
count = len;
- vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE);
-
/* We can write back this queue in page reclaim */
current->backing_dev_info = mapping->backing_dev_info;
@@ -437,6 +437,7 @@ xip_file_write(struct file *filp, const char __user *buf, size_t len,
current->backing_dev_info = NULL;
out_up:
mutex_unlock(&inode->i_mutex);
+ sb_end_write(inode->i_sb);
return ret;
}
EXPORT_SYMBOL_GPL(xip_file_write);