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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 /fs/ext4/dir.c
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>
Diffstat (limited to 'fs/ext4/dir.c')
-rw-r--r--fs/ext4/dir.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/fs/ext4/dir.c b/fs/ext4/dir.c
index 374510f72baa..ece76fb6a40c 100644
--- a/fs/ext4/dir.c
+++ b/fs/ext4/dir.c
@@ -39,7 +39,7 @@ static int ext4_release_dir(struct inode *inode,
struct file *filp);
const struct file_operations ext4_dir_operations = {
- .llseek = generic_file_llseek,
+ .llseek = ext4_llseek,
.read = generic_read_dir,
.readdir = ext4_readdir, /* we take BKL. needed?*/
.unlocked_ioctl = ext4_ioctl,