usb: gadget: mass_storage: fail fsg_store_file() early if colud not open file
Currently, when a new value is stored to the “file” sysfs entry, fsg_store_file() will release existing backing file and only then attempt to open a new one. If that fails, no new backing file is open. This commit changes the fsg_lun_open() so that it closes existing backing file only after the new backing file has been successfully opened. With that change, fsg_store_file() may use it to perform an atomic open operation with guarantee that logical unit will either point to the new backing file or still to the old one. Signed-off-by: Michal Nazarewicz <mina86@mina86.com> Acked-by: Alan Stern <stern@rowland.harvard.edu Signed-off-by: Felipe Balbi <balbi@ti.com>
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@ -617,6 +617,16 @@ static struct usb_gadget_strings fsg_stringtab = {
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* the caller must own fsg->filesem for writing.
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*/
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static void fsg_lun_close(struct fsg_lun *curlun)
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{
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if (curlun->filp) {
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LDBG(curlun, "close backing file\n");
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fput(curlun->filp);
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curlun->filp = NULL;
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}
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}
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static int fsg_lun_open(struct fsg_lun *curlun, const char *filename)
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{
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int ro;
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@ -626,6 +636,8 @@ static int fsg_lun_open(struct fsg_lun *curlun, const char *filename)
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loff_t size;
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loff_t num_sectors;
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loff_t min_sectors;
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unsigned int blkbits;
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unsigned int blksize;
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/* R/W if we can, R/O if we must */
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ro = curlun->initially_ro;
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@ -670,17 +682,17 @@ static int fsg_lun_open(struct fsg_lun *curlun, const char *filename)
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}
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if (curlun->cdrom) {
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curlun->blksize = 2048;
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curlun->blkbits = 11;
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blksize = 2048;
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blkbits = 11;
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} else if (inode->i_bdev) {
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curlun->blksize = bdev_logical_block_size(inode->i_bdev);
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curlun->blkbits = blksize_bits(curlun->blksize);
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blksize = bdev_logical_block_size(inode->i_bdev);
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blkbits = blksize_bits(blksize);
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} else {
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curlun->blksize = 512;
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curlun->blkbits = 9;
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blksize = 512;
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blkbits = 9;
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}
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num_sectors = size >> curlun->blkbits; /* File size in logic-block-size blocks */
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num_sectors = size >> blkbits; /* File size in logic-block-size blocks */
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min_sectors = 1;
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if (curlun->cdrom) {
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min_sectors = 300; /* Smallest track is 300 frames */
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@ -697,7 +709,12 @@ static int fsg_lun_open(struct fsg_lun *curlun, const char *filename)
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goto out;
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}
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if (fsg_lun_is_open(curlun))
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fsg_lun_close(curlun);
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get_file(filp);
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curlun->blksize = blksize;
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curlun->blkbits = blkbits;
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curlun->ro = ro;
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curlun->filp = filp;
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curlun->file_length = size;
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@ -711,16 +728,6 @@ out:
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}
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static void fsg_lun_close(struct fsg_lun *curlun)
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{
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if (curlun->filp) {
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LDBG(curlun, "close backing file\n");
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fput(curlun->filp);
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curlun->filp = NULL;
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}
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}
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/*-------------------------------------------------------------------------*/
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/*
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@ -871,19 +878,18 @@ static ssize_t fsg_store_file(struct device *dev, struct device_attribute *attr,
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if (count > 0 && buf[count-1] == '\n')
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((char *) buf)[count-1] = 0; /* Ugh! */
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/* Eject current medium */
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down_write(filesem);
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if (fsg_lun_is_open(curlun)) {
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fsg_lun_close(curlun);
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curlun->unit_attention_data = SS_MEDIUM_NOT_PRESENT;
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}
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/* Load new medium */
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down_write(filesem);
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if (count > 0 && buf[0]) {
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/* fsg_lun_open() will close existing file if any. */
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rc = fsg_lun_open(curlun, buf);
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if (rc == 0)
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curlun->unit_attention_data =
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SS_NOT_READY_TO_READY_TRANSITION;
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} else if (fsg_lun_is_open(curlun)) {
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fsg_lun_close(curlun);
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curlun->unit_attention_data = SS_MEDIUM_NOT_PRESENT;
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}
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up_write(filesem);
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return (rc < 0 ? rc : count);
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