From e0d10bfa91b0a089a9e2c378b5c42f4e96171d95 Mon Sep 17 00:00:00 2001 From: Toshiyuki Okajima Date: Wed, 27 Oct 2010 21:30:06 -0400 Subject: [PATCH] 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 ; mount -t ext4 #2: mkfs.ext3 ; tune2fs -Oextent,huge_file ; mount -t ext4 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 Signed-off-by: "Theodore Ts'o" Cc: Andreas Dilger --- fs/ext4/dir.c | 2 +- fs/ext4/ext4.h | 1 + fs/ext4/file.c | 44 +++++++++++++++++++++++++++++++++++++++++++- 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, 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, 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; /* file.c */ extern const struct inode_operations ext4_file_inode_operations; extern const struct file_operations ext4_file_operations; +extern loff_t ext4_llseek(struct file *file, loff_t offset, int origin); /* namei.c */ extern 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) 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, -- 2.11.4.GIT