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author | Toshiyuki Okajima <toshi.okajima@jp.fujitsu.com> | 2010-10-28 05:30:06 +0400 |
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committer | Theodore Ts'o <tytso@mit.edu> | 2010-10-28 05:30:06 +0400 |
commit | e0d10bfa91b0a089a9e2c378b5c42f4e96171d95 (patch) | |
tree | 254d6b0b7d7ca2dfd817171d8d641c1a648e9c46 /fs/ext4/file.c | |
parent | c41303ced67c4ebf51bf2e7d0f139155e09e0939 (diff) | |
download | linux-e0d10bfa91b0a089a9e2c378b5c42f4e96171d95.tar.xz |
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>
Diffstat (limited to 'fs/ext4/file.c')
-rw-r--r-- | fs/ext4/file.c | 44 |
1 files changed, 43 insertions, 1 deletions
diff --git a/fs/ext4/file.c b/fs/ext4/file.c index ee92b66d4558..5a5c55ddceef 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) return dquot_file_open(inode, filp); } +/* + * ext4_llseek() copied from generic_file_llseek() to handle both + * block-mapped and extent-mapped maxbytes values. This should + * otherwise be identical with generic_file_llseek(). + */ +loff_t ext4_llseek(struct file *file, loff_t offset, int origin) +{ + struct inode *inode = file->f_mapping->host; + loff_t maxbytes; + + if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))) + maxbytes = EXT4_SB(inode->i_sb)->s_bitmap_maxbytes; + else + maxbytes = inode->i_sb->s_maxbytes; + mutex_lock(&inode->i_mutex); + switch (origin) { + case SEEK_END: + offset += inode->i_size; + break; + case SEEK_CUR: + if (offset == 0) { + mutex_unlock(&inode->i_mutex); + return file->f_pos; + } + offset += file->f_pos; + break; + } + + if (offset < 0 || offset > maxbytes) { + mutex_unlock(&inode->i_mutex); + return -EINVAL; + } + + if (offset != file->f_pos) { + file->f_pos = offset; + file->f_version = 0; + } + mutex_unlock(&inode->i_mutex); + + return offset; +} + const struct file_operations ext4_file_operations = { - .llseek = generic_file_llseek, + .llseek = ext4_llseek, .read = do_sync_read, .write = do_sync_write, .aio_read = generic_file_aio_read, |