2007-12-14 17:59:17

by Eric Sandeen

Subject: [PATCH] export iov_shorten for ext4's use

ext4 needs to deal with 2 different max file offsets for block- and
extent-allocated file formats, whereas the s_maxbytes scheme can only deal
with one. So, for block-allocated files, we must catch and fix up
too-large offsets from within the filesystem.

Having iov_shorten exported allows such things as:

if (pos + length > sbi->s_bitmap_maxbytes) {
nr_segs = iov_shorten((struct iovec *)iov, nr_segs,
sbi->s_bitmap_maxbytes - pos);
}

to fix up too-large writes to these files in ext4_file_write().

This patch is currently living in the ext4 patch queue.

Signed-off-by: Eric Sandeen <[email protected]>

---

Index: linux-2.6.24-rc3/fs/read_write.c
===================================================================
--- linux-2.6.24-rc3.orig/fs/read_write.c
+++ linux-2.6.24-rc3/fs/read_write.c
@@ -451,6 +451,8 @@ unsigned long iov_shorten(struct iovec *
return seg;
}

+EXPORT_SYMBOL(iov_shorten);
+
ssize_t do_sync_readv_writev(struct file *filp, const struct iovec *iov,
unsigned long nr_segs, size_t len, loff_t *ppos, iov_fn_t fn)
{

2007-12-17 15:14:29

by Eric Sandeen

Subject: Re: [PATCH] export iov_shorten for ext4's use

(And, take 2... follow the coding style on export declarations...)

ext4 needs to deal with 2 different max file offsets for block- and
extent-allocated file formats, whereas the s_maxbytes scheme can only deal
with one. So, for block-allocated files, we must catch and fix up
too-large offsets from within the filesystem.

Having iov_shorten exported allows such things as:

if (pos + length > sbi->s_bitmap_maxbytes) {
nr_segs = iov_shorten((struct iovec *)iov, nr_segs,
sbi->s_bitmap_maxbytes - pos);
}

to fix up too-large writes to these files in ext4_file_write().

This patch is currently living in the ext4 patch queue.

Signed-off-by: Eric Sandeen <[email protected]>

---


Index: linux-2.6.24-rc3/fs/read_write.c
===================================================================
--- linux-2.6.24-rc3.orig/fs/read_write.c
+++ linux-2.6.24-rc3/fs/read_write.c
@@ -450,6 +450,7 @@ unsigned long iov_shorten(struct iovec *
}
return seg;
}
+EXPORT_SYMBOL(iov_shorten)

ssize_t do_sync_readv_writev(struct file *filp, const struct iovec *iov,
unsigned long nr_segs, size_t len, loff_t *ppos, iov_fn_t fn)