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authorToshiyuki Okajima <toshi.okajima@jp.fujitsu.com>2010-10-27 21:30:06 -0400
committerTheodore Ts'o <tytso@mit.edu>2010-10-27 21:30:06 -0400
commite0d10bfa91b0a089a9e2c378b5c42f4e96171d95 (patch)
tree254d6b0b7d7ca2dfd817171d8d641c1a648e9c46
parentc41303ced67c4ebf51bf2e7d0f139155e09e0939 (diff)
ext4: improve llseek error handling for overly large seek offsets
The llseek system call should return EINVAL if passed a seek offset which results in a write error. What this maximum offset should be depends on whether or not the huge_file file system feature is set, and whether or not the file is extent based or not. If the file has no "EXT4_EXTENTS_FL" flag, the maximum size which can be written (write systemcall) is different from the maximum size which can be sought (lseek systemcall). For example, the following 2 cases demonstrates the differences between the maximum size which can be written, versus the seek offset allowed by the llseek system call: #1: mkfs.ext3 <dev>; mount -t ext4 <dev> #2: mkfs.ext3 <dev>; tune2fs -Oextent,huge_file <dev>; mount -t ext4 <dev> Table. the max file size which we can write or seek at each filesystem feature tuning and file flag setting +============+===============================+===============================+ | \ File flag| | | | \ | !EXT4_EXTENTS_FL | EXT4_EXTETNS_FL | |case \| | | +------------+-------------------------------+-------------------------------+ | #1 | write: 2194719883264 | write: -------------- | | | seek: 2199023251456 | seek: -------------- | +------------+-------------------------------+-------------------------------+ | #2 | write: 4402345721856 | write: 17592186044415 | | | seek: 17592186044415 | seek: 17592186044415 | +------------+-------------------------------+-------------------------------+ The differences exist because ext4 has 2 maxbytes which are sb->s_maxbytes (= extent-mapped maxbytes) and EXT4_SB(sb)->s_bitmap_maxbytes (= block-mapped maxbytes). Although generic_file_llseek uses only extent-mapped maxbytes. (llseek of ext4_file_operations is generic_file_llseek which uses sb->s_maxbytes.) Therefore we create ext4 llseek function which uses 2 maxbytes. The new own function originates from generic_file_llseek(). If the file flag, "EXT4_EXTENTS_FL" is not set, the function alters inode->i_sb->s_maxbytes into EXT4_SB(inode->i_sb)->s_bitmap_maxbytes. Signed-off-by: Toshiyuki Okajima <toshi.okajima@jp.fujitsu.com> Signed-off-by: "Theodore Ts'o" <tytso@mit.edu> Cc: Andreas Dilger <adilger.kernel@dilger.ca>
-rw-r--r--fs/ext4/dir.c2
-rw-r--r--fs/ext4/ext4.h1
-rw-r--r--fs/ext4/file.c44
3 files changed, 45 insertions, 2 deletions
diff --git a/fs/ext4/dir.c b/fs/ext4/dir.c
index 374510f72ba..ece76fb6a40 100644
--- a/fs/ext4/dir.c
+++ b/fs/ext4/dir.c
@@ -39,7 +39,7 @@ static int ext4_release_dir(struct inode *inode,
39 struct file *filp); 39 struct file *filp);
40 40
41const struct file_operations ext4_dir_operations = { 41const struct file_operations ext4_dir_operations = {
42 .llseek = generic_file_llseek, 42 .llseek = ext4_llseek,
43 .read = generic_read_dir, 43 .read = generic_read_dir,
44 .readdir = ext4_readdir, /* we take BKL. needed?*/ 44 .readdir = ext4_readdir, /* we take BKL. needed?*/
45 .unlocked_ioctl = ext4_ioctl, 45 .unlocked_ioctl = ext4_ioctl,
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 4c5fe37b237..e1c01552a3d 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -2006,6 +2006,7 @@ extern const struct file_operations ext4_dir_operations;
2006/* file.c */ 2006/* file.c */
2007extern const struct inode_operations ext4_file_inode_operations; 2007extern const struct inode_operations ext4_file_inode_operations;
2008extern const struct file_operations ext4_file_operations; 2008extern const struct file_operations ext4_file_operations;
2009extern loff_t ext4_llseek(struct file *file, loff_t offset, int origin);
2009 2010
2010/* namei.c */ 2011/* namei.c */
2011extern const struct inode_operations ext4_dir_inode_operations; 2012extern const struct inode_operations ext4_dir_inode_operations;
diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index ee92b66d455..5a5c55ddcee 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -130,8 +130,50 @@ static int ext4_file_open(struct inode * inode, struct file * filp)
130 return dquot_file_open(inode, filp); 130 return dquot_file_open(inode, filp);
131} 131}
132 132
133/*
134 * ext4_llseek() copied from generic_file_llseek() to handle both
135 * block-mapped and extent-mapped maxbytes values. This should
136 * otherwise be identical with generic_file_llseek().
137 */
138loff_t ext4_llseek(struct file *file, loff_t offset, int origin)
139{
140 struct inode *inode = file->f_mapping->host;
141 loff_t maxbytes;
142
143 if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)))
144 maxbytes = EXT4_SB(inode->i_sb)->s_bitmap_maxbytes;
145 else
146 maxbytes = inode->i_sb->s_maxbytes;
147 mutex_lock(&inode->i_mutex);
148 switch (origin) {
149 case SEEK_END:
150 offset += inode->i_size;
151 break;
152 case SEEK_CUR:
153 if (offset == 0) {
154 mutex_unlock(&inode->i_mutex);
155 return file->f_pos;
156 }
157 offset += file->f_pos;
158 break;
159 }
160
161 if (offset < 0 || offset > maxbytes) {
162 mutex_unlock(&inode->i_mutex);
163 return -EINVAL;
164 }
165
166 if (offset != file->f_pos) {
167 file->f_pos = offset;
168 file->f_version = 0;
169 }
170 mutex_unlock(&inode->i_mutex);
171
172 return offset;
173}
174
133const struct file_operations ext4_file_operations = { 175const struct file_operations ext4_file_operations = {
134 .llseek = generic_file_llseek, 176 .llseek = ext4_llseek,
135 .read = do_sync_read, 177 .read = do_sync_read,
136 .write = do_sync_write, 178 .write = do_sync_write,
137 .aio_read = generic_file_aio_read, 179 .aio_read = generic_file_aio_read,